A chance to enjoy a couple of pints, cheaper than the pub.
All the ones I have been to have been in Pubs and you buy your beer at the standard bar price. Where are folk clubs that run their own bars?

Edinburgh Folk Club used to meet in a bar run by Edinburgh University Students Association (temporarily closed for refurbishment of the building). It had the cheapest beer I know of in the Edinburgh city centre. Quite why EUSA thought it was a good idea to subsidize students getting sloshed I wouldn't know.