I'd like the selling interval to ramp up to a quicker pace as you sell more and more units. Considering the hoard/blowout-sale nature of the main moneymaker, smithore, it would speed the auctions lategame.
If this is done, then selling to the store needs to be done one player at a time, not all together, just like any other type of trade. This is so people can choose to back off with an exact amount when the numbers are flying by.