How does the average indy fed make any money?

[MoFo]

Whenever I see a clip of an indy show, even the well established ones like PWG/CZW, it seems like theres not many people there at all, and they must only be paying a max of like $20 to get in anyway.

With a card of about 15-20 ppl, a place to hire to host the event, etc, there must be a substantial amount of money to pay so how is this made?