The rule with my Mum was that as long as we were studying, she'd support us, but if we finished/quit uni, then we had to pay board. I don't remember how much it was (early 90s), but it was more than fair. We also had jobs from when we were 15 & had to buy our own clothes, entertainment with that.

We always thought we were so much better off than those kids who never grew up, lived with their parents into their late 20s/30s and never learnt to look after themselves. We always thought people like that were pretty useless and it still annoys that my taxes are paying for their unemployment benefits, the bludgers.