You need to be specific about the paint prep.
Will the old paint be stripped off? Or sand and paint over?
Depends on the condition/age of the old paint.
I painted helicopters in the 1970-80's. Back then about $10000... now I can't even guess, probably more than twice that.
Make sure the painter understands and has experience with helos, very easy to permanently damage the helo in numerous ways.
slowrotor