I would say minimum for a full detailing kit would probably run you about $400-$500. Figure Porter Cable, various pads for it, clay, car wash, wax, polish, fluids for cleaning windshield, wheels, tires, leather, etc. and a lot of towels.Magna said:
Rip can confirm this, but PC may save you an 30 to 1hr off your detail time. It may be more efficient because you don't get nearly as tired, but you still do have to be patient and spend time.
$500 would be roughly 2 full (interior and exterior) details, and what would that get you through...? Spring and Fall.
Assuming you go to a good detailer, the advantages are experience, and access to equipment and cleaning fluids that you wouldn't normally have. If you don't trust yourself polishing, I would recommend a pro. If you don't have the time or the resources, go with a pro as well.
However, there is something to consider... while a detailer makes his living off making cars look good, I personally think they are never going to give your car the love and respect that you give it.
It's important to visit the detailer a few times prior to going there. Watch them wash a few cars, esp. dark colors. Look at finished cars and inspect the job. If you don't like it, you shouldn't go to them.
For what it's worth, I'm going to head to a detailer this spring because I'd like a few paint chips taken care of as well as having my car professionally polished. Since I have no garage to work from, I'm not comfortable with doing touchup work like this while competing with the environment.
I'm still probably going to get the Porter Cable and various equipment though, because in the long run, I'm planning on detailing my car a lot more than I plan on visiting a detailer. At the very least it'll make it easier to apply and remove wax.