i suppose it's all relative to what you can afford but here are a few of the prices they tend to stick to in London (STG£ prices)
Babe Station girl - £250 - £350 per hour
Babe Station girl that has done one or two scenes - £400 per hour
Gonzo Star - £500 per hour
I see that Aletta Ocean is currently touring London and is charging £1,000 per hour.
I don't see why one would pay that kind of money just because she's a porn star, far better looking ladies on this site IMO.
Where do you find these girls mate??