I think parking at hotels is very common now, Loews, Hyatt, Days Inn, everywhere.
We paid $19 a day to park at a run-of-the-mill Days Inn five years ago in Savannah. Even our local Hyatt charges its guests parking fees. It's been a few years, but I remember they tried to charge DH & I $40 for an overnight stay. What was interesting with that one is they sell spots to locals for parking downtown. I already pay $89 per month there so I can park downtown close to the courthouse. $40 per night (or two days) is outrageous, IMO, especially when so many locals already use their garage for monthly rentals.
But whatcha gonna do? I still think that even with $15 per night, it's still a massive savings for a comparable onsite vacation at one of the parks in Orlando.