2. The relevant meaning for this particular discussion is "in a position to spend $200 on a thermostat but not willing to spend thousands". That seems like pretty much exactly the bracket a lot of US software people would be in.
(There is a phenomenon in US politics where people earning $300k/year think they are "middle class" and I agree that that's silly. But software developers on ~$100k? Middle class. No question.)
Median household income, 2008-2012 $53,046
http://quickfacts.census.gov/qfd/states/00000.html
If we're talking globally, software engineers are even further to the right end.