Recently, I was talking to some fellow grad students and the issue of money came up. I was shocked to find out my two friends who are TA's in the philosophy and physics departments at the same university make $600 less than I do per month. They make about $1100/month while I make almost $1700/month as a TA in the math department. I know $600 doesn't seem like much, but I make roughly 1.5 times as much as them! All three of us get the same tuition waiver and pay roughly the same in fees. Also, my previous roommate who was a TA in the music department got paid about $1100/month, but this was over two years ago while I was still an undergrad. Is this consistent with all other large universities, especially at this magnitude? If it is, why do you think so?
My explanation is that the math department has more "power" and can fight for better paid TA positions. What I mean by "power" is that despite the relatively small size of the math department, math is more central to other majors. For example, everyone in STEM and many people in economics, business, finance, etc. take a multitude of math classes and give the math department more leverage when it comes to funding. Also, you don't need expensive equipment to do math research so essentially all funding goes towards salaries.
I could also be completely mistaken so if someone would kindly explain how universities generally fund their departments that could also help enlighten me.