My friend and I have definitely thought about how it might be nice to have automated trading. In the end, I don't think it's a good idea though. A better idea would be to introduce an independent Demand system (the "Bid" of a Bid/Ask system) to complement the Supply system. This would flip everything on its head: the buyer would be the one making a listing and the seller would be the one who can "buyout" the listing in an instant by providing the proper in game item to fulfill the demand.
With this in place, it would become possible for players to quickly sell items (to other players who aren't in such a hurry and will benefit from better prices). It allows players with time (the Market Makers) to interact more efficiently with players who aren't interested in spending hours on the Auction House (the customers).
This wouldn't really let you clear out thousands of cards in a day, but would speed up the process by an order of magnitude.