A 15 hour yfz450 for $2900 is a steal. One bit of advice though, look it over with a very critical eye as if it's got 200 hard hours and just got cleaned up for the sell.
I don't trust any seller's hour meter claims unless it is hardwired into a vehicles original gauge cluster. Even if it's an honest estimate off the top of their head, it's probably waaay off.
Look closely into the areas that someone wouldn't be able to clean easily. Also tell them not to run it before you come see it. You want to start it cold. All in all it seems like a killer deal, but you've still gotta be careful.