..It all depends on what you are doing....
I clean them all year round and the best thing I do is give the option of a wash and wax or a full T.F.R. going over.....
Small wash and wax.....£40
Medium wash and wax......£55
Large wash and wax...£70
Small TFR, wash and wax.....£60
Medium TFR wash and wax....£75
Large TFR wash and wax....£90
Wash and wax is simple.....I use normal good quality car wash and wax....extending brushes...low pressure..
TFR is more time consuming however you charge for it so there you go.....
Be very careful though where you point the pressure lance as conny`s are not watertight on the roof panels..I used to fit them so I know.....I use steam cleaners in my outfit and find the hot water does the trick at low pressure with some elbow grease....
Hope that answers your question...