I do bodywork for a living and do complete paint jobs. We just painted a 71 Plymouth GTX and between myself and another guy we had 20 hours in blocking for paint alone on the body, not including the doors, hood, fenders and trunk lid. I did a rough estimate with my boss and the prep and paint work alone comes to about $5500. This is at a labor rate of $65. Thats not even including the amount of work we have into getting everything straight. The total paint job and body work will probably come to 15,000 including the extensive amount of body work that was done. All I have to say is you get what you pay for. The $3000 job is probably going to be a quick sand and spray, nothing ridiculous. Where the $6000 job is probably going to be a really nice paint job with alot of work put forth to make it straight and really nice for you. Do most of the work yourself, such as taking the handles out, door locks, moldings, quarter windows, bumpers, doors, fenders, trunk lid, hood etc and the cost of the job will drastically drop. A color change is a very in depth job and requires a ton of work. It's up to how you want your car to look.