seller etiquette

My wife sells things occasionally on fb marketplace.  Pricing is agreed to upfront.  Probably 65% of the time people try to renegotiate when they pick it up.

Unfortunately, you are in the minority (as am I) that your word is your word.

I can't fault the seller.

I'd second what Mitch2 says. And event though a fair proportion of participants will treat our specialized markets as communities, there will still be traders that will prioritize any sale over respectful arrangements. 

At the other other extreme is Facebook Marketplace - a total Wild-West of a trading place. To lock in a deal - you have to show up with the money, on-time; offer to pay a reasonable deposit with Venmo ahead of pick-up; or get a firm commitment from the seller that they will hold, like "Will you hold for 3 days until I can get there in person?". This latter approach can be a bit hit or miss - I have lost out a couple of times because of it.

So, the two things you could do differently next time are 1) pay a deposit with PayPal/Venmo, 2) get a commitment from the seller that they will hold for 3 days, even if another offer comes in. 

Best of luck in the future .... 

@parkergetdean 

You said in your OP that he reached out to inform you he had another buyer and could you pay ASAP? And you didn't read the email until the next morning. That's kind of on you, don't you think. 

I'm sure you are a trustworthy guy and would have certainly followed through. But in my many years of buying and selling, that is not always the case. 

When buying I always make some kind of good faith down payment to be sure the item is reserved for me and as a seller request the same to hold an item.

@ozzy62 +1

The seller sends OP email, the OP does not respond, the OP is surprised and offended!? Really?