It is very possible that revenue is a secondary driver for the parking decision. This could be driven by other factors, such as limiting access to the garages at night when there are a significant number of cars (and people) still in the area... I have a friend who was an uppity up at the mouse (before he retired) that once told me that while charging for parking makes significant revenue, the real reason there are parking fees is because it helps deter crime in the parking lots. But I could be wrong. It has happened before.