You should check flights to LA on priceline and all those sites. Last time I was on Virgin's website they had them for like $60-80 one-way between SF/LA. IDK if that's still out of your range, but might be worth looking into. (Before submitting, I did a quote of leaving SF late afternoon/early evening and returning Sunday early evening and RT was $156. Other fans might be up for sharing hotel rooms if you want to save on lodging.)
I just checked Priceline and the cheapest round trip airfare would be $130. The price for my seat in the stadium would be about $55, bringing my total to $185 (but I would definitely have to eat, so it would at least be $210).
Unfortunately that would still be out of my price range, for 200 dollars is 2/3rds of what I typically get every two weeks. With classes coming up I don't think I'd be able to save any money to attend them.
Many thanks to you for trying to help me! I guess my time to watch the USWNT play in person hasn't come yet.