The fact that you don't see it is part of the problem. You took a bunch of charity here (folks helping you value/identify/etc the watch), and are selling it. You were given a gift, and now you're profiting off it. So yeah, people are disappointed.
I would look at you with a better light if you were a good contributor and either gave someone who really wanted the watch an opportunity to get a deal, or only really looked into it because you wanted it, not to make a buck. OR, if you DID want to make a buck, actually did your own darn'ed research and figured it out yourself.