The concept that better performers should be paid more. Most assume that the current zero minus expenses arrangement is meritocratic, but it isn’t, not in a musical sense: it rewards bands who bring large numbers of people, not bands that perform well.
In most contexts, meritocracy does not require that the minimum be zero minus expenses, although for some reason that’s expected in most/many music clubs.
Contrary to popular belief, Fair Trade Music is not anti-meritocracy: bringing the minimum up from zero minus expenses does not breed complacency: we’ve never met a musician who would be content to perform for minimum wage. Additionally, nobody wants to play to an empty house; bands are unlikely to stop promoting their shows.