Think of it as an integrated VPN, anyone can own and operate one. They charge like any other node in the network so they can make money or at least cover costs.

The main issue is one of trust, we have left it up to the user what exit nodes to add to their system beyond a few we ship in the firmware run by ourselves.

Personally I think this is a point of weakness long term, we need to decide on criteria for including other exit servers. Trust is hard