Posted By:
Scott MI don't have a problem at all with anyone "holding" back knowledge that they've gained over the course of their collecting experience regarding what they feel the scarcity of a particular card or set is.
If another collector is attempting to collect that particularly rare card or set, they'll find out soon enough just how scarce it is because they never see it come up for sale or, when it does come up for sale, it'll likely go much higher than "book".
If looking at this from the sellers perspective and they don't have the knowledge of the rarity of a particular card or set then I would agree with others comments that the seller needs to research and know exactly what they are selling. If nothing else, the seller will still likely be pleasantly surprised when their rare card sells for "book" or more...
Scott