It really depends on the quality of work! I mean this is a bit like asking:
How much do you want for your car?
£100
£1000
£10000
£100000
etc
It depends on what the car is like! I mean if the work was top quality, say £50 an hour, easy to do, hassle free and compact; then that's a lot better than £15 an hour, difficult to do, and lots of hassle.
I've only sold work once, but I sold it at 3x the monthly value since it was low quality. It was either that or give it away.