I pay $5 a trade. Idk how it would get cheaper for him to use an MM
It has nothing to do with commissions. You pay the MM a fee. He works off your order throughout the trading session, or over several sessions. The idea is to affect stock price as little as possible.
In Pennyland, you see it done mostly by toxic lenders or other insiders with large amounts of stock to dump. But naturally it can be done the other way round.