If they are big sellers they will probably have a lot of buyers and find that listing the item at one dollar is the most effective way to get a good final price.
They could well be playing the averages game, not that important if you lose a few dollars on some items, so long as you make it up on others and then end up with your nose in front at the end of the load.
Starting their items at the low entry price will be excellent marketing fro them as well, as anyone in the market will be looking at what they have to offer.
What you start the auction at isn't important, it's what the final sale price is that's important, so starting at a dollar doesn't mean that they won't get the $26.00 or whatever.
You also have to consider what they are buying them for also, if they are big sellers then you could be talking about container loads at a time, and that will be giving them a big advantage with lower prices.