What makes a fair deal

Well, that was fast! I did a post yesterday about some vintage tees I put up for sale on eBay, and after I posted it I went to bed. I woke up this morning and I already had one offer. It was an offer for $10, that was half my asking price, so I countered with $13. A couple hours go by and BOOM! Another offer. This one was from another user, and it was for $15. I jump on it, because it may not have been my full asking price, I thought it was fair.

I know I could've held out for my full asking price, but why? The shirt doesn't fit, so why not flip it quick, so I can buy more items to resale. So far this has been the fastest flip I've done on eBay, less than 12 hours.

This means I may have undervalued the tee, but I did check similar sales and listings. I priced it based on that, but I couldn't find the exact shirt, and it was a 2x, which increases the value. I could have priced it higher, and I know it would have eventually sold, but I want to build a reputation as a seller who gives fair prices. At the end of the day the retail game is won by selling products as quickly as possible, and building a good rep, not how much you can get for your product.