new clutch/gearbox price

How much might a new clutch or gearbox cost?

From time to time, I hear talk of installing a new one for whatever reason, eg:

'Oh, he's riding the clutch, he'll be be forking out the money for a new one.'

Bad habits aside, how much might they actually cost?

Don't worry too much about the gearbox, as a courier i did 110k in the first two years of having my cb500.
I replaced the clutch friction plates and springs at 85k and that was all that was required apart from normal servicing and the odd cable.
As the company ran a fleet of cb500's and never had a problem with the gearbox/clutch on any of them to my knowledge you should be able to feel confident with it.