Honestly...thats kinda the way it is when you enter into something like that. Any type of artwork on a 1:1 car must be cleared over. If you do something say...just on the hood, your still sanding, prepping and painting the entire hood. Then wet sanding a buffing it to match the rest of the car...add in the cost of the actual artwork, whatever that may be...it can get really pricey.
It's very hard to put a dollar amount on complete custom work, alot of times it is done on a time and material basis.