Earlier quoted context omitted.
At my institution the 9-month pay was less than $25k per year (from 2010-2016) with subsidized housing (still pretty expensive) and family on MediCal when my wife worked part time. How are you going to replace 50 TAs with full time employees? Class sizes were already 700 students in basic calculus and up to 300 in engineering calculus.
The median household income in California is $77.5k [1]. I'll emphasize household. Your 9-month pay was for 20 hours, that means $25k is actually $66.6k annualized which does not include your subsidized housing nor for inflation. The economics just simply is not there. Sure, students might be able to squeak 10-20% in wage increase at the cost of all other university voluntary support such as student group support and…
Also, seems like you are completely ignoring the actual "labor" that the graduate students provide for their research labs. The number of professors in Computer Science at MIT who actually writes code at least once a week may shock you, but the truth is, for MIT to be on the top of the food chain someone needs to keep the wheels turning.