Most public transportation routes lose money since farebox revenues don't cover the operating costs and the overhead related to the system. Naturally, lower ridership routes lose more money than higher ridership routes, and evening service has lower ridership than service during the day. I don't know how full the trains are to the complex during evening events (they seemed pretty full when I used to take them...50+ years ago), and so I don't know how much money SEPTA loses on those express services. I suspect they still do lose money, and since they are not regular services, SEPTA probably incurs higher labor costs for operators, station personnel, and probably extra security, due to the need to pay overtime. So running the services to the complex on game nights is still a money losing proposition even with higher than average nighttime ridership.
Even though I'm in the transportation profession, my expertise is not in funding transit service, but I know that funding sources vary substantially across the country. Pennsylvania seems to be in worse shape than many other places that have dedicated sources including portions of fuel or sales tax revenues. Fuel taxes are wildly unpopular almost everywhere, in large part because most people don't ride transit. In Pennsylvania, there are large areas where nobody or almost nobody rides. Even though, as you point out, drivers benefit from decreased traffic, it's not a tangible benefit for them.
