What changes the price
Scope
One panel, several panels or the whole car.
Prep and repairs
Dents, rust and failing clear coat must be fixed first.
Color
Same color is simpler than a full color change with jambs.
Finish
Pearl, candy and custom finishes take more layers.
Vehicle size
More surface, more material and time.
Cheap paint jobs
Very low prices usually mean minimal prep and little clear coat. It can look fine at first and start failing in a summer or two. Read luxury vs standard paint.