Buying used when you should have bought new...

Some time ago I bought an item off Audiogon. I personally picked up the item. The price was right and the item was as described. Deal done. No problems with the seller.

The item lasted a few months before it started to act up. It needed repair. It had no warranty so I searched for a retail dealer to get the item fixed. I found a dealer, but they refused to service the item because it was not purchased through them. Ok, I searched for a repair shop which was tough, but I found one of high reputation that knew what they were doing.

I picked up the item today and it sounds great.

However, after what I paid the seller and then what I paid for repair, I could have almost purchased the item new for a couple more bucks.

What items, if any, should be bought new, if possible, and what items can be bought used to be safe? Is there a guideline of some kind?
Definitely buy a phono cartridge new.
Cables and power cords are usually the safest used buy.
I guess I've been lucky so far, as I've only one bad experience in 5 years here (knock wood).

I always buy new phono cartridges. The stylus is usually a large amount of the price. The condition of a used stylus is a wild guess. Even a super honest seller may not be able to tell either.

If I buy used tube gear, I usually assume I'll have to replace the tubes immediately, unless there is a clear indication how old the tubes are and the seller has good feekback.
I agree with the two previous comments, and would add CD/SACD players to the list, since lasers have a finite life.

I think the decision to buy used vs. new also hinges on whether you can get a good discount price on the new item. For example, I was able to buy a Denon DVD-3910 player earlier this year (through an authorized dealer) for about 1/3 off full retail price, which was only a bit more than buying the same unit used.
Too bad about your experience with the used transaction... I have found it really depends more on the manufacturer of the component, rather than the type of component. I've been lucky with my transactions in that the manufacturers have always stood behind the products:
Cables: I bought a pair of used Audience Au24 cables that were too short for my rig, I re-sold them w/o ever hooking them up to a member who found out that one of them was faulty, I offered him a refund, instead, he chose to send back to Audience and they repaired it free, no issue.
CDP: Resolution Audio offers a service where you give them the serial # of the used unit and they will reply to you with the component's history of its age, # of owners and repairs, they hapily service used units.
Speakers: Even though I bought my Green Mountain Audio speakers new, they offer warrantee for life on their products even to owners who buy used, really unbelievable.
Amps: Cary has been a pleasure to deal with. I bought my amps used and they were missing some chassis screws on the bottom and sides, called Cary and sent out the screws the next day, free. Later I had some upgrades done, they gave me a great deal despite the fact I wasn't the original owner.
There are a lot of great companies out there that offer tremendous service. Although, I'm sure I'll hit a product or manufacturer eventually that I'll have an issue with, so far I've been fortunate.
I generally like to buy new. Get the best you can afford and just keep it and don't trade to much. When I have issues, my dealer always loans me something. I never go with out sound. I have a few friends that have gone with out tunes for 60 days while things are getting fixed.

My equipment has been very reliable, like one issue in the last ten years due to defect. But, I've sent it back a few times for upgrades, thought a issue...but was bad tube etc.
If you're a dealer for a product line you should assist anyone who needs a repair of that brand whether they purchased from you or not. People do move around and shouldn't be penalized because they bought the product in a different area of the country. Also, the used market is an integral part of high end audio. It would be a poor business practice to turn away any actively buying audiophile just because they purchased on the used market. If anything dealers and manufacturer should turn 2nd buyer service request into a profit center operation.

The "you get what you pay for" is still valid. While the potential for really great deals is possible, buying second hand is always riskier than buying new from an authorized dealer. For the most part the risk is manageable and is reflected in the sale price.
A dealer who only services what they sell is a jerk and a poor business person. Does he think you will return? If the dealer would not assist you then you should contact the manufacturer. You might not have a warranty but they are obligated to service what they sell.

Used stuff generally sells for 1/2 retail. Buying used is a bit of a crap shoot, and I doubt I would spend $500 for a used item that retails at $1,000 when I could probably buy it new for closer to $800, but once you get into the higher end the savings are significant. I got my speakers used for $10K and a new pair would be over $20K with sales tax. I stretched to pay what I did. Retail would have been impossible.

I agree with most of the above. Buy used stuff that is relatively new. Buy new cartridges and factor a tube replacement into the price of a used piece. Don't buy old digital players, motors and mechanisms wear out. Be careful with old analog, motors and bearing last a long time but could worn. Paying retail for cables is insane. Even though I wouldn't want any, SS stuff is a pretty safe bet.

Even if this one piece was not the bargain you had hoped for, in the long run if you are careful you will come out waaaaaaaaaay ahead buying used.
I always lean to buy new for the fair price.
Phono carts I only buy new.
Tube gear is simple to troubleshoot so I can buy it used.
...btw I would add motorcycle to buy-new list.
My first rule is to buy the best stuff, from the best places at the best price you can get. Then if you have a problem it won't be a problem to get it resolved. As the saying goes "The quality is remembered long after the price is forgotten." My second rule, if buying used the feedback rating is the most important thing. Yours or their integrity or feedback is everything. Buying from a good seller can introduce oneself to a much higher level of gear than you might be able to afford otherwise. I would tend to buy gear new that has wear items in it such as tape transports,cd players etc. They can often be found at the best discounts. Used from a high feedback seller for pre-amps,amps and speakers and such. And whatever you buy, obtain items that are not older than five years old. Time can affect anything for the worse.
As mentioned above, used equipment should average about 50% or less of the retail price, while new equipment can often be found for 80-90% of retail. Therefore your savings from buying used should generally be about 40% off retail. One thing not mentioned yet is the added cost associated with buying used items you have not auditioned, then finding they do not work in your system. Sometimes you can break even when reselling them, but other times you will be down at least the shipping costs, unless you can afford to wait for the right buyer. If you like the cost savings from buying used, there are ways to reduce the risks, such as buying from reputable sellers (good feedback or dealer demos), buying more recently made equipment (which should not have significant wear or parts failure problems), and buying from still-active manufacturers who offer repair (and possibly upgrade) service on their equipment. Your example of using an item for a "few months" before it started acting up is unusual, and indicates the piece was probably working fine for the previous owner. Sounds like simply some bad luck on your part. I wouldn't give up on purchasing used, but you have to decide your own comfort level.