It really varies a lot based on a few factors:
-How rich is the school (and department/program)
-How much do they value you & how receptive they are to graduate student associations (GSA's).
-Stipends vary a lot across fields. Humanities are paid low. I'm in molecular bio, and I'm paid ~$4-8k more than folks in ecology at my school.
-Cost of living at location.
I chose UT Austin. Package had a stipend of $40k, health insurance (fully paid for and its good), I can add dental and vision ensurance on my plan for a decent price, no student fees. That's real damn good for molecular bio stipends, similar to stipends at places with much higher COL like California schools.
My other offers:
Rice SSPB. Stipend 35k, not really good health insurance that i had to pay (i think) around $600 yearly on. No dental insurance. $600 yearly student fees. Only 1 TAship I'd need to take on, the rest would be RA funding.
ASU MCB. Stipend 32k. I believe fully funded health insurance (not good benefits), but I got this offer late and had already accepted another so I didn't properly consider it. 50/50 RA/TA for my funding during the entirety of my degree. Thank God I didn't go with this offer, because I know I'll be a terrible TA wherever I go.
CU Boulder Biochemistry: Stipend 36k. Mostly subsidized health insurance, like Rice, with ~$600 yearly cost. No student fees. High cost of living.