I would say anything that make the vinyl not lay flat on the platter. And a warp does not make the record playable. Yes it doeas affect the price i.e if you have 2 copies of a record infront of you, at the same price, one has a warp and one doesnt you will but the one without a warp. Therefore, the price has to be reduced on the warped copy (obviuosly the rarer the record the more the price difference between good and warped reduices).