+4 for a few reasons...
Pro painting is expensive, looks great, and should be done if you simply want that particular bike to be painted, or the frame is worth a second life. As far as what happens after you paint, be prepared to simply accept the paint job expense as what it takes to keep the bike going or make it the way you want it.
Powder coating is much cheaper, and is gaining on the paint pros all the time. It's cheap enough here that I'm going to try and get the expense out of a couple of flips. The flips will not be to people who want a particular bike, but to someone who wants a great bike in a certain price range with a level of components in mind. In this way, I can re-use frames I'd otherwise give away or discard.
Restoration painting is a whole other ball game. Cost is not the issue, results are.
Rattle-can painting is a temporary, decent fix if you happen to be good enough at it so it doesn't look like a rattle-can job. I'm not. Bob Barker is.
Some bikes simply are great but have crappy paint jobs. I won't mention brands, but Gios and Pinarello come to mind. In those cases, the frames are good enough to stand the expense, and the paint isn't that intricate.
Custom paint on bikes, like custom paint on cars, is not a value enhancement, it's a personal choice or project. Done well enough to a high-level bike, it can enhance value, just like a Jesse James motorcycle or car... it's art, craft, and aesthetic. Dr. Deltron comes to mind.
Touch-up, though painstaking and tedious, can turn some really battered frames into decent bikes. It takes patience, time, and follow-up with rubbing compound, wax, etc, but often gets pretty good results for just labor and a small amount of materials.
I'll always have a couple bikes that are worth powdercoating if they get really torn up. I generally can't afford the level of bike that is worth a repaint, and I'm not up for one just for the sake of the project. However, I'm always looking....we're optimists here, or we wouldn't be always on the lookout for that one bike, eh?