Thats the MM's making money...
Lets say bid is .18 and ask is .20. You buy the stock at a limit price of .20 but there is a "hidden ask" at .19. The "hidden ask" will print because it is the best offer at .19, then the MM who routed your order will print the .20 and charge your broker ( you ) .20 and keep the .01 for himself.
He's playing the spread, also just becuase you see the bid/ask at a certain price DOES NOT mean that someone has orders in at those prices. MM's can display whatever price they wish, ultimatly thier job is to insure the price is at a range that will yeild the most volume.
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