Of all the LPFM stations around the country I have known about or spoken with, the income ranges from about $500 a year to around $200,000 a year. The $200,000 a year is in essence a small market LPFM that is the local station operated much like a small town full service station with high school sports and local news.
There are quite a few operating in the $10,000 to $30,000 a year range doing a mass appeal hometown station format.
I would say the vast majority of LPFM stations operate on under $10,000 a year in income. Many simply stop trying to get funds once they have covered their bills. For some that's $200 to $300 a month.
Some of the Christian stations have virtually no income and are funded out of the church/ministry budget.
By the way, one Christian station operates from the board president's home and has 2 twenty dollar a month underwriters. They've operated for years this way. They play local and regional artists in certain hours and run a few old time radio shows in their mix. They have never pushed for funds and the two underwriters actually found them and asked to sign up.