"Upper-middle class" may have been a better description for tech worker incomes, on average. Which I'm sure you know caries a very different cachet, socially and politically, than "middle class"
Basic point being (and more germane to the thread as a whole) "middle class" as a label for tech workers is clearly off base.
72k isn't even 'upper-middle'. You have been backpedalling all over, and in another comment even claimed 50k was the number for 'middle class'. You have no idea what middle class means or you are trolling.
The real upper class laughs at you guys arguing amongst yourselves over what qualifies as "middle class" and "upper middle class" and "upper lower middle class" and "lower middle upper middle class". So silly.
The context of this sub-thread (starting 3 up from here) clearly referred to "salary", a.k.a. personal income. The two categories are, of course, very different. Which explains the great bulk of the noise in this discussion.
You might want to read things more carefully before accusing people of backpedalling and trolling, in other words.
SF Median household income is 77k, average is 104k. Earning 72k does not put you in the upper class, not in the slightest.