Keep in mind that living costs are higher in some places than others, and salaries tend to vary accordingly. Most universities in the US probably pay their TA's and RA's enough for basic living expenses in their cities.
I don't have any direct experience with current conditions, but when I was a graduate student about 25 years ago I shared an apartment with another student, didn't own a car, and wasn't into nightlife or partying, so I was never short of cash. I was even able to travel to Europe twice, staying in hostels and with friends and relatives.