Everyone has different prices. What you can get for them is what you should price, its the same with windows.
I charge them the same as i do windows approx 1 to £1.50 per window. 3 metres by 3 metres, with a metre high foundation wall, so that approx 9 panels of glass, so approx £10. Roofs, take longer its depends if glass or not. So charge is more.
Roof if glass, 3*3 metre conservatory = 3*3*3 = £27 without finials
Roof if plastic 3*3*2 = £18 without finials
I'll add more if finials are present like £5. Then it comes down to how dirty the conservatory is in the first place, if its green its probably double my charges, cos its a ruddy mess, and time consuming, if its regular work, 1 or 2 times a year then my charges above apply as it wont be so time consuming to clean.
Then it also comes down as to what style the conservatory is. Smaller windows & more of them and more framework = more work = higher price.
I know some people charge alot more than what ive put.