Face the fact that as a professional musician (if you are) you are competing with people who are doing it for the crack and already earn a fat salary as teacher,librarian, social worker or whatever. This is not a problem dustmen have, there is no queue of people wanting to be a dustman for £30 a day (and bring your own van).
   But in the end it's supply and demand and the market place. If you can put £500 of ticket sales in the club. you'll get something like 80% of it, plus whatever profit you can make on the CD sales. That's how it evens out. Unless of course you have connections with the subsidied world of funders/arts boards etc, in which case the sky's the limit and you're paid according to how brown your nose is prepared to get.