I just want to point out that even when no profit motive is involved (as in the case of a Folk Club or society) the equation of how much people will pay to see a particular artist vs how much the venue can offer to pay him/her still holds true - unless of course there is some wealthy person willing to subsidize gigs purely for their artistic merit. Also, it's impossible to judge whether or not a venue is making an "excessive" profit. You don't know what their costs are. The conditions of every gig are worked out according to the needs of the performer and the venue, and can depend on a lot of things. For example, a well known, well paid performer may agree to do a gig - house concert, or something of that sort, for much less that their usual fee if they are on the road and need to fill a vacant night. And the person/venue that provides this gig may not be 'ripping' the artist off at all. They know they can only attract/accommodate a small audience, therefore can only offer a modest fee.