I used to feel the same way you did, THEN. . . .
I painted my own car. Now I'm much more sympathetic to the prices these shops charge for body and paint work. I'll grant you, there are a lot of shady guys out there that are taking advantage of folks, but the shops that are reliable and do good work are usually worth the money.
Keep in mind, if you're talking to professional shops, that these guys feed their kids, pay their bills, and (most likely) pay the mortgage on their business with the labor costs they charge you. It takes a lot of money to make a living painting old cars, and that's why so few guys are out there doing it.
For the most part, it's just simple math. When I was going through paint/body on my 77, I loosely kept track of the hours I was spending. We VERY CONSERVATIVELY estimated just shy of 230 hours from first sheet of sandpaper to completion. The shops in my area with good reputations charge between $50-65 and hour (most are closer to $65 than $50):
230 hours X $50/hour = $11,500.00
My materials cost right at $2100.00, so total cost would have been, roughly, $13,600.00 had I shopped the car out. I will tell you this number is consistent with the three estimates I got on the car before I decided to paint it myself. Truth is, I seriously doubt I could have gotten the job done on my car for $13,600.00 at a professional shop. We did a lot of work on the car that I didn't account for in my estimated hours (TOTAL hours are quickly approaching 550).
I'm not defending every shop out there because some of them really are outrageous, but the truth is that really good body/paint guys are hard to find and they're in high demand. Blame it on Rides, Barret Jackson, or just all the baby-boomers burning through 401ks. The truth is, there are more guys out there wanting to "restore" old cars than there are good body men. The result? Higher demand and higher prices for the guys who do know what they're doing.
You're best bet is to do the car yourself if you have the time, patience, skill, location, and tools to do the job right. If not, just keep in mind that paint and body work, like most things, operates under the old addage "You get what you pay for". If the price seems to good to be true, you can be sure it probably is. . . .
J