Not sure what you mean by average, but if you assume someone is a mediocre computer scientist because the dont work in C, well I just hope thats not what you mean.I like to emphasize the fact that the "mainstream" software development world of "average" computer scientists/software engineers does not reflect the entire market.
Yeah this may be different from area to area, but generally as an engineer of any kind, you will start off at about 50-60k and peak at about 100-110k. Java developers as a mean in this area make 81k a year. For people doing computer engineering things, its the exact same number and scale, C/C++ jobs are the same thing.In many cases, I see the lower-level, software/hardware engineers writing these embedded applications making far more than your average Java/.NET developer...
I think the reason being is that most major companies have "bands", and pay is based on that, and all engineerings fall under a certain band, now once you go into management, being a director, thats when you are looking at 150 to 300k depending what you do. If you go work for a corporate company as a technical grunt, you will not make much more than 100k, no matter what your field is. (there are of course exceptions to the rule.)