Kinda had my entirely resprayed.... paid £300 for it but thats due to contacts aswelll as other things.
Basicly , most of the charge in a spray is the working hours it takes (about 6 days 9-5) But you can make it easier for em which will make it cheaper. With mine , the only thing i wanted them to do was paint the outer "visible" shell , while id paint the inside of the engine bay (you cant get behind the engine , unless you can afford to have it taken out) , inside of boot & doors.
Doing these bits urself saves alot of time as masking up these parts is what takes most of the time anyway , took me about 5hours per door. Anyways after all this , my car was only in there for 3 days since half of it was already done.