I did the same in my university days. A semester-long parking pass (4 months) was around $900, daily parking was $12. A ticket was $25 if paid in the first 7 days. They checked cars and ticketed twice a week, on random days, but always twice a week (I assume this was a contract stipulation). I parked there four days a week, I'd usually get one ticket a week, sometimes two... still cheaper than paying daily or for the pass. They'd only tow if you had overdue tickets, so as long as I paid them immediately it was all good.
Sometimes it pays to do the math.