Are stock trade commissions evidence of anti-competitive practice? A typical commission on a typical stock trade these days is $8. I don't understood how it can cost this much. It looks like the entire process is happening in software, electronically, and so the actual cost to the parties that supply this service should be near zero. 

So I'm wondering, where does that money go? Is someone making a profit? Are they protecting that profit with exclusive dealing, collusion, or some other anti-competitive practice?
The money goes to banks/brokers. In fact most of the revenue in the financial sector comes from fees like that.

This is to compensate the bank/broker from taking the risk of carrying the opposite position on their books for a while, and the labor put into actually trading for you. A part of it is probably also profit. Since there are large entry costs, one would expect the financial sector to earn  profits.