It is producer dependant, not venue (although some venues do produce some of their programming in house of course). Doing a similar sized roll at the same venue but for different producers can have massive variance in pay packet, in my experience from say purely profit share to half what you might get in the West End. Additionally a bigger more successful fringe show may pay peanuts compered to a much smaller one. And you'd be amazed at the names willing to work for very little.
Annoyingly, some producers who did pay more have cut their rates to be in line with Equity's minimum, so I have more often found myself worse off because of.
EDIT: and sadly is doesn't mean minimum wage. At 28 hours of minimum wage it would cover a working week (just about...), but not rehearsals or tech periods.