The median household income in the US is about 26,500 after taxes. That’s roughly 500 a week, and a tithe would be 50 a week.
A church of 100 people would have roughly 25 households, so their giving would be about 1250 a week.
That’s about 65,000 a year. No one is getting rich.
Assuming they give their pastor a standard of living equivalent to their own, that would take 500 a week + social security + med + health + pension. Let’s make it 800. That leaves 450 for building utilities and church programs, to include widows and orphans.
It’s possible they retain merely a preacher instead of a pastor, and he has another job to support himself and his family, so he would simply receive whatever their hearts led them to believe was the right thing to do for him.
They would still have the costs of building + utilities, but they should have more money for programming, to include outreach.
Your numbers are interesting, but the average attendence of US churches is about 200 while the average membership is much larger.
Your numbers are true for a church of 100 but that is not the norm.
Only about 20% of members of an average church attend regularly so if there are 100 in attendance then there are likely 400 to 500 members. That would make your number of $65000 actually more like a quarter million on the low side. Surely with that income a pastor could support himself, the property and have some left over for charity.