I was a window tinter for 8 years in a previous life and can add a bit of insight. Especially since I just bought my Aveo earlier this week and tinted it the other night
Pricing - will vary greatly depending on what part of the country you are in. Around here, an Aveo would run between $150-$225. More on the coasts and where legality is an issue.
Installation - the quality of the installation can vary widely as well. Ask around to find a quality shop. Also, a good trick is to call the high end car dealers. Your local Chevy dealer uses a tint shop because they are the cheapest. Your local Ferrari, BMW, Mercedes, Lexus, etc, dealers user a local shop because they do a quality job and they don't want to have to deal with screw ups on $100,000+ cars. Also, when talking with a shop, question the installation of the rear window. Both the 5 door and sedan have fairly curved windows (even if they don't look like it). Some shops will install the rear window in 2-3 pieces of film. A quality shop will heatshrink and install in one piece.
Film Quality - This is one of the primary things that effects the cost of a decent tint job. A tint shop can have a higher profit margin by using "seconds" or low quality runs of films. If you've ever seen purple tint, bubbled or blistered tint, these are all results of cheap film. The best (and most expensive) film brands are 3M, Formula1, and Huper Optic. LLumar, Madico, Sungard, etc. are OK too, but a step below the big boys. I personally recommend 3M. I mean, 3M makes the best adhesives in the world and their window film is no different.
If you are going to do it yourself, I recommend using the static cling stuff. At least if ya screw it up, you can just pull it off and try again.
Stay away from the pre-cut kits on ebay. The film is worthless and every car is different and should be custom cut. If anybody needs tips on do it yourself tinting, I'll be happy to answer any questions.