I think it was one of his brothers' wands? Bill or Charlie's? I got the impression (maybe from the movies) that it was broken and had been badly repaired, so Ron got it while the older brother got a new one with money from his new job...?

Yeah, that always struck me as weird. I guess we're supposed to take it as Ollivander being kind of a weirdo even to wizards, or something, but... yeah, I don't know. I didn't get a lot of that from the book, though, again, it's all Harry's perspective.

I guess maybe there's more than one wand that can fit the wizard?

Edit: person above me said what I was thinking, except more coherently and with better info anyway. :)