The profit is with low volume in bids and asks they can move the price and manipulate, you can profit doing it either direction. You try and have the public gap fill and sell high or buy low. its super easy if there are only 20 or so shares seperating .88 and 1.15 on the ask side.
It's not that easy. You always run the risk that someone with high volume undercuts you and then you're screwed. Especially when your avg share price can be calculated.