Because we all know it's the miners who are buying up all these cards. But for some reason the difficulty is trending down.

You can see just how many of these recently purchased 6970s are mining by looking at the next difficulty prediction. If we did drive them out of stock it was a poor purchase decision it seems, because we're pushing it back towards 1784732 at the moment. Maybe if you wait a few days you'll be able to buy an open box version cheaper when all the panic sellers return some hardware.