Quoted from Slim64:My guess is they are higher value and more desired. This keeps people there longer to increase potential bidders on the not so desirable items. Sell off all the best stuff first and it'll turn into a ghost town quick.
This is exactly the reason for it. While they are not always last, they are probably never going to be first. You would lose half if not more of your crowd if you jumped right to the high-end items.