it's a tricky question to answer. basically it's a musicians pension..
I remember a few years ago stevie wonder was on about £1,000,000 a year on royalties for the sales of his work
you get money from licensing for tv and films also (moby's play album. he got as much for that as he did in sales. AND it's a free advert)
depends though, some people will take a discounted rate OR give permission for no royalties if it's a new song and they wanted it played.
a station has to play more than 40 seconds for it to get royalties.. some organisations will come to agreement with the artists for a "bulk" license.. or they will give a one off fee for multiple plays.. and a lot lower royalty rate.
but if it's no agreement, it's between £40-80.. it's very hard to say the EXACT amount due to agreements.
I do hate certain producers who rip off others work and feel they are above paying the ORIGINAL composer royalties. thats theft, and they aren't above the law, they should be made to pay. Heres one that annoys me >
http://www.youtube.com/watch?v=M4KX7SkDe4Q
he picks people from outside the US work to use, as to contest it you have to go to America.. sampling is all good as long as it's creative and not a blatant rip off.
it's dealt with with agencies such as PRS..
even club dj's in the UK have to submit a playlist.