I think that's because there is a limited amount of the stuff it stocks so even when they're randomly chosen they tend to end up being the same items. Goblin Bazaar only stocks common and uncommon items from a small level range and there aren't hundreds of those.
Okay, last time and then I'll let the thread quietly die - but I just wanted to say that I finally got a second Bejeweled Shortsword, and it only took an additional three weeks (!!!). That's after the randomness goblins taunting me by putting two in the club rewards, of course. I am content, now, since I don't have enough to devote to more than one per fighter in my two-fighter build anyway. ...at least, until the level cap is raised and we get more ...but hopefully around that time we'll get another shop and I'd just be able to BUY #3 and #4. Or something.