This hundred quid thing is ridiculous. When I ran my father in laws bar, we would book bands and stuff, and paid up to 500 quid for unknown people (average was around 200 for a couple of hours, but we did have a few at the higher end, some did it for 80). I know a pub is a bit different to a club, but clubs can easily afford 5k especially if they will be packed due to the person appearing.
I know for a fact that powerhouse pays in the thousands for appearances from people who have been on TV. I know this as I know the manager and a while back they paid 4k I think it was for an ex factor contestant..and not even one of the really popular ones. I think it was Aiden grimshaw (I was pissed off she didn't tell me that actually before it happened, as I loved him
)