I had to do the body work myself because I couldn't afford to have someone else do it. Bartamos, you are right- 95% of the work is everything you do before the paint goes on. Materials alone for a single stage paint job cost me more than $1600.
2 gallons of quality paint (with all mixers) was about $600. Epoxy primer is also expensive. Hi-build primer, fillers (that you load up and sand off that end up on as a pile of dust on the floor and you apply it all over again, over and over), rolls of quality sand paper and flexible hand sanders, special foam discs & compounds to cut & buff, chemicals to clean & prep the metal and cleaners to prep in between primer layers- it all adds up fast. And that doesn't include the paint guns, the compressor, and the filtering system you need to get really clean air.
I will say that I could never have imagined how many hours of sanding and re-priming and refilling and sanding that I was in for- it was a downright painful process, and mostly because of how many times I sanded too deep (hitting metal) and having to re-epoxy to seal yet again. There is no way to learn it without getting a feel for it, and getting a feel for it has taken a LOT of time (and money). And I still don't know even a 1/3 of what I want to know about body working and painting. I would guess that a talented & experienced body guy could have spent 25% of the time that I spent, and had better results than me.
Maybe my next project will go quicker.