Most of them should be, according to C3 at least, in pretty good shape.
Basically the "discount" you're getting is the price of the warranty, which you're not getting. Saving $150+ on a nearly new board is pretty good. Chances are that you won't wreck it, anyways. OTOH, if you're the type of guy who goes through 2 or 3 boards a season, you might want to hold off on pulling the trigger on a board with no warranty.