OK, what's the protocol?

So, you provide an honest quote for shipping on an item and the actual cost is less. Are you:

A) Obligated to provide an unsolicited refund regardless of the overage
B) Obligated to provide a refund only if solicited regardless of the overage
C) Obligated to provide an unsolicited refund only if over a certain amount.
D) Obligated to provide a refund only if solicited AND over a certain amount
E) Never obligated to provide a refund under any circumstances

And by obligated, I mean obligated by the rules of decorum established here or by the values of a gentlemen whichever are more conservative.
I personally will give my best estimate, and if it's less refund the difference, if it's more within reason, I pay it.
I would consider the actual cost of driving to send the package, and such.
If the charge for shipping was over more than a few dollars, I would offer the buyer a refund.
If it was less than a few dollars, I would count it as gas money.
In some cases folks charge a bundle for "time spent" and expect to make money on the whole thing...
Other kindlier folks just want the buyer to enjoy the product as much as they themselves did.
A Gentleman would ofer the refund of the extra cash for shipping. And a Gentleman or Lady would decline the offer.
Also if the shiping chare was too low, and you had to pay out of pocket.
A Gentleman would politly mention the extra cost, but tell the buyer not to worry. And a Gentleman or Lady buyer would insist on paying the extra charge, and the seller should gracefully accept.
Let your conscience be your guide.
I refund the difference.
Gas money today is probably more than a few dollars!
I think it greatly depends on the overage. For instance you quote 89.00 and the shipping is 20.00. If you ship ups or fedex then the client will not ever know so your final shipping price would be up to you, then your will make a determination of how you treat your customers.

But If you spent 3 hours packing the article and 20.00 for packing material and 1 hour driving to send the package away then make sure you dont cheat yourself. You know whats fair just let that be your guide.
Good advice from everyone thanx. After further thought, I'm still haven't come to conclusion but here's $.02 to my own post. I have woefully underestimated shipping many times in the past and have just eaten it. I know I have over paid for shipping on things coming my way too in the past. If I over estimate for things I'm shipping doesn't it all just come out in the wash if you've been doing it long enough?? I figure where I underestimated my costs or over paid in the past, those were numbers I agreed to and so can't complain about either way. Is shipping supposed to cover JUST shipping cost or actual time and material to pack and deliver on my part???? More questions.
Your underestimation, and eating of shipping costs in the past, does not
mean diddly to your buyer who is being asked to pay more than he/she
should. IMO, shipping costs should also cover the cost of shipping
materials, i.e. a Handling fee. That's the way every retail merchant
charges for shipping and handling, and buyers of used gear should
welcome paying a little extra for excellent quality packing including
double boxing and the proper packing materials. So, be sure to include
an appropriate amount to cover any additional packaging expenses you

Bottom line, if you feel any guilt about not refunding a shipping overage
(and I'm not talking about $5 here, unless it's on a small item like tubes),
then you should refund the dough.

Anyway, just one man's opinion.
Many items on ebay "feature" outlandish shipping fees. Trading here implies a kinder, more ethical group of enthusiasts who are in it for the love of the game, not the pursuit of the almighty dollar. There are all kinds from all walks of life. The fact that you asked at all is a good thing. Remenber that in the scheme of things, shipping costs are but a fraction of the value of the goods and therefore should not bear too much on the deal, as long it is reasonable and fair to all. So I wouldn't fret too much, unless the buyer was taking issue. FWIW, I have acces to boxes and shipping materials here at work and don't charge for that, but it does take time to properly package an item, do the do on the shipper's website, and shuffle off to FedEx. Taking the time to do these things myself gives peace of mind, and assurance to the buyer.
I generally quote shipping and handling as a charge on top of the price of the item. I normally include enough extra $ (usually $3-5 depending on weight and packaging complexity) to make sure I don't end up eating FEDEX charges; but nowhere close to a fair cost for my labor, gas, and packaging.

If the deal was negotiated as covering only exact shipper charges, then I would refund that, but only in that case which I would avoid because it's just not worth the effort IMO.

Please, I don't really have time to split hairs on shipping costs.
"Your underestimation, and eating of shipping costs in the past, does not mean diddly to your buyer who is being asked to pay more than he/she

No, but, it will influence my personal shipping policy formulations. If I'm willing to refund, I should be willing to ask FOR a refund. 'Not sure I'm ready to do that. Also, Im only asking them to pay what we both agreed to.

I think if it is a material miscalculation it should be refunded. Otherwise, I think it all washes out.
First, underestimation of shipping.

There is no reason for a quote to be grossly inaccurate if you have original packaging. You have the weight and size of what is to be shipped and online calculators are available from the shippers. In view of this, if my quote is too low, it is likely to be miniscule and I will absorb the difference.

On the other hand, if the shipment requires that you package with new shipping materials as you do not have the original, there is more time and effort involved, and a greater likelihood of error. In this case, if the underestimation is more than a couple of bucks, I would go back to the purchaser in advance of the shipment and explain why shipping will be be higher and request an adjustment of price. I will offer to cancel the transaction if the purchaser is unhappy about the unforseen development. They will know that you're not lying or using a trick to get out of a transaction because they can confirm the price on an online shipper's calculator with the weight and dimensions that you supply to them. They would also see the price of shipping on the shipping invoice when they receive it. I think this is a proper, businesslike approach. Still, even if this is a proper business aproach, this is a bit uncomfortable on a personal level and there is a certain feeling of community here on AudiogoN. So I would try to avoid this and be careful not to give shipping estimates until I knew for sure what they would be. By the way, the potential abuse of this latter approach is one of the reasons why many jurisdictions have laws requiring people to charge no more than their original estimates in a commercial setting.

Now, how about the other way around,what if I overestimate.

If I overestimate, no matter how small it is, I send the difference back to the purchaser without solicitation. The goodwill to your reputation far exceeds the couple of bucks of gas money. In fact, the smaller the amount, the more upstanding it makes you look. And the extra money is not something you were expecting anyway, so no loss to you.

Now on the issue of shipping costs, let me tell you what made me livid once. Every once in a while I need a good rant. I requested a shipping estimate via a specific method of shipping with a specific company. The seller sends the quote. I verify it with the online shipping calculator, confirm and send the seller the money. The seller then sends via a different, cheaper method than what I specifically requested and paid for. It was even with a different company. He then pocketed the $100 difference in his favour.
I think we're essentially on the same page.

It's easier in the long run to calculate the shipping costs up front and add $5 or $10 for materials. It's not that diffcult to find the manufacturer's shipping weight and calculate cost.

If one ballparks these figures, then one lives by the estimation and moves on.
OK, here's what happened. I quoted a package of CDs to Singapore. USPS website quoted $20 for parcel post. Today, PO lady charged me parcel envelope rate (because of dimensions and weight) of $12.95. Not lots of money to me but initially I thought, hey for once I'm not getting screwed (I usually quote to low when I send something.) and it's only about $7.00 - not to mention I didn't charge for the minimal packaging, time effort etc. (Not much really.) Anywho, as a percentage, of total shipping quote and item price ($27.00) It think it's material and I'm going to return the difference.

Thanx all.
Pawlowski6132, I have had similar experiences with the USPS online quote versus the price at the counter when shipping internationally. I use the USPS all the time, but their rates are damn confusing.

Recently, a Canadian transaction partner quoted me the appropriate price for some tubes I was mailing, yet all the info on the USPS website pointed me to a postage amount that was nearly triple the actual cost.

I refunded the excess postage to him, too.
I for one in many instances have paid over my quoted shipping price. And yes I agree about Ebay sellers asking way to much for shipping many an item.
It's your call, but I think you are doing the right thing refunding the difference. Besides, for a paltry sum, you probably feel better and I know that the recipient will really enjoy the fact that he dealt with a good seller. Win-win in my view.
Well how much are we talking about. You can ship right from your computer and know exactly how much it will cost.