$50 bucks is the going rate for every professional instillation. You might be able to find someone off the street to do it for $30, but if they screw something up, what are you going to do? Atleast if you pay the $50 at BBY or CarToys, you're covered incase something happens during the install...
This is where is comes down to money or quality.
A good in-dash unit with bluetooth, av-out puts, and ipod would be the JVC AVX44. It usually runs $500, but it's going to last you much longer than cheap-o Jensen, or Dual.
If you are looking for something in a double din, I would look at the...