just a thought, I was a pro, now a semi-pro(due to finances) singer I have been on local and national radio and regional tv in several areas. All to do with singing I hasten to add, however as I am not a "Big Name" I have organisers contact me and ask me to travel (one time) over two hundred miles to perform at their club and they say £75 is the going rate. I'll let you do the maths (Travelling alone 3hrs there 3hrs back). If they said a guaranteed £75 against a percentage of the door it could add up to something worth travelling for. I would like to point out that most organisers do a "Professional" job even though they may be "Amateurs"
and it has been my pleasure to make friends with many of the organisers I have come into contact with

As a footnote: you can imagine the dismay when you have performed at a club for less than £100 pounds because it's the going rate, the audience X door price easily amounted to much more. and then the next guest night they have a "Big Name" who certainly don't do it for less than £100 and you know that the club has made a loss on them. Is this a type of subsidy.