I go to house concerts often, maybe 4-6 times a year. I rarely pay more than $20 for a concert, and I feel that's a bargain if the concert is good. If I were attending the performance of a big-name performer, it would cost me $50 or more; and the performance might not be as good as a house concert
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So, pnelson, if you've got qualms - buy CDs.

Yes, this is pretty much the strategy I've adopted to assuage my conscience.   Go to house concerts (in my area the Folk Song Society of Greater Boston has them) and buy a CD.   It will hurt my brain to try to work out how buying a CD of an artist from Maine, USA is going to help pay back unknown artists whose accents are clearly, say, Northumbrian or Australian, but maybe in those places they've stream-captured some unknown folk artist with a "down East" (Maine) accent so they buy a CD of a local and it all balances out somehow.   At least I hope so.

Thanks, everyone, for your comments.