I have had this done alot, I did 2 different bumper swaps on my Talon, along with getting the oem front repainted (5 bumpers total), plus I had my Accord front repainted.
I have paid anywhere from $200-400 per bumper. I only had one bad experience where a small amount of paint lifted but they were not any cheaper, just not a great shop, didn't do a lot of research.
I would not pay more than $300-400 tops. This should get you a better than OEM paint job, match perfectly. It's just a matter of finding the right shop. I have 2 body shops in 10 minutes I trust, maybe 4 more that I know that are good, just haven't needed to use them. Get estimates, you will find they are all over the board.
Look at what types of cars are on the lot, if you see a bunch of beaters, probably stay away. If you see nice cars, don't think it's all good though, many are going through insurance and don't have a clue. That's also a good indicator of a medicure body shop, ask them to do something non oem, if they say they don't do it, they may not be good (though some just don't care to do custom work, even for a bunch of money, they don't have the time/resources).