If you believe in the principle of tithing, then you believe that you will be blessed in return for your sacrifice, so much so that God will open the windows of heaven, and the blessing so large, "that there shall not be room enough to receive it."
So really, BYU fans should have MORE to donate than other schools because those fans aren't being blessed through tithing...
I get it, I'm in your same situation with a family on one income and struggling to make ends meet, but I've also seen my parents and all of the folks from their rich Ward in Sandy who have been blessed tremendously blessed.

Compare BYU to Alabama or Mississippi. The state of Utah and specifically Utah county has been blessed much much more financially than Tuscaloosa or Oxford. Utah's economy is booming. Maybe you don't feel it right now, but their are PLENTY of wealthy Mormons who can afford to pay more and don't.