I believe you have to factor in what kind of spray painting work will be done to your wheels. If the design of your wheels have different edges and you want multi colour then it will cost more. I have done cheap wheel sprays before too but that is the same color for the whole wheel so I suppose that wouldn't be a tough job.
You have to add labour for removing the tyres off the wheels and they need to use more paint for the center portion of the wheel. Most cheap wheel sprays only spray the parts where it is not covered by the tyres. I believe $1000 may be a little expensive but not really to the extend of carrot price. It depends on the quality of the work and when they tell you 2 to 3 days, probably the work that will be done may exceed your expectations as compared to cheap wheel sprays.