$100k/year is very much in line with what an actual sociologist would describe as middle class. Most of the upper quintile is part of the middle class. Most sociologists describe the top 1-5% as upper class. The next ~45% is middle class, then the next 30-40% is working class, then the remaining 10% or so is poor/lower class[1].

The upper class is made up of capitalists, high-level executives and people with inherited wealth. People who work in professional occupations such as doctors or engineers are not part of the upper class.

[1] http://en.wikipedia.org/wiki/American_middle_class#Academic_...