It doesn't only vary on who it is, it varies on the size of the church, how big the city is, etc.

There are some visiting preachers that end up giving the local church money, rather than accepting money from them.

Some small churches will give $50, $100, $300 per service depending on their ability. Some churches don't even get enough in to pay the church electric bill, let alone pay tithes, parsonage, visiting preachers, etc.

Also, $100 sometimes isn't even enough to cover the costs of the trip, unless it is very close to their home. Some preachers don't worry about the money... some won't share their "word from God" unless they get X number of dollars... (kinda like a gunslinger for hire in the Old West).