How much does it cost to refinish a door?

there isn't enough info on this, does the door need a shell or skin? how much repair, what kind of car, is it two or three stage paint, i could go on and on......more info plz, ie, yr make model 2 or four door, 2 or 3 stage, size depth of dent...estimates are generally free at any body shop go by and get one....