Have something like, items in the AH's that don't sell are removed from the game & become available to drop again.
This would stop over pricing of items. Since if items aren't priced to sell instead of being priced at what people want to get for those items. It would increase the amount of potential buyers for items & have more players buying gold. It would give players the impression that drops have increased even though they're picking up someone else's junk.
There's also a good chance it would stimulate the games economy so the price of gold starts to climb, making items worth more.