£300 - £500? Interesting.
Let me quote you the example of a well-known trio who were invited to a club in the North East for £150.
As they live in scattered locations throughout the South(ish) of England, this would have taken three days out of their lives and cost that much in fuel.
Did they take the booking?
Could they afford to take it?
Clearly not.

Re: dressing rooms. I was appalled to hear about a 16-year-old young woman performer who was told to change behind the bar 'because everybody else does'. And I didn't mention hotel accommodation. I'm talking about artists who have driven a hell of a long way from home and who are simply waved off after the gig. Surely someone on the organising committee has a spare room or at least a sofa?