I'm wondering why he said he would not take it to bare steel but the price depends on what is underneath?
What paint system is he using? Is he billing you on time and materials? What is his labor rate and how many hours is his estimate for? Have you seen any of his work? What is his time line? Is he giving you anything in writing?
A good paint system is going to cost close to a grand for the color alone if he is using base clear. Materials add up fast....