If you are able to walk a few minutes I'd just park in the Stout Street carpark instead. That's where I usually go for a stadium event. $8 for weekend, or after 5pm on a weekday and it's virtually across the road from the train station.
It's usually where I park or in this area, but that's not really the point. The issue is the disparity between the pricing offered.
Other advantage of parking elsewhere like Stout Street is getting out much quicker. Don't know what it's like for a Phoenix game as have never parked at the stadium for one, but did for the for the Ed Sheeran concert - weeknight and a sellout so figured it was safer to have a confirmed carpark booked rather than find other options already full when we got there. They held everyone in the carpark until all the people on foot were out so we ended up having to sit in the car for nearly 2 hours afterwards. Probably not like that for a Phoenix game with a much smaller crowd though.