Why would Mark Hamill asking for money be cheapening himself?

I'm not in the U.K so I did not watch this but this is a tv program right. Channel 4 no less. They sell advertising space in between breaks. So essentially they're making money off the Star Wars brand and the likes of its stars like Mark Hamill and their work. Why shouldn't he get paid? Channel 4 are.

It would be like one of the many conventions asking Hamill or any other Star Wars actor to appear for free when the organisers are making money off ticket sales.

Speaking of conventions, I've never been to one but from what I'm aware of most of the actors that appeared on this tv special appear regularly at Star Wars conventions. So it's not really a great big reunion except its on tv.