(I posted this as a comment to someone else's review of sportsbuy, but it qualifies as a review itself:)
SportsBuy is also a lousy place to sell cards. They've got a user interface that seems as if it were intentionally designed to make listing cards as difficult and time consuming as possible. They often don't bother to even acknowledge feedback or suggestions. Selling a card for $0.25 results in $0.92 worth of transaction and "payment processing" fees (which I guess they justify by taxing the buyer $2.10 for shipping and "buyer protection"). And I suspect that a privileged few sellers get first pick of buy offers before the rest of us get a chance to see them.