This is not uncommon. I have heard of this in several buildings especially if the garage is separate from the condo building. You also pay taxes on your parking space as well.
Much like a condo building, the parking garage is going to require maintenance (snow removal, elevator repair, staff, insurance, etc.)
Walter J. Burns
1 Newark St.
Hoboken, NJ 07030
201-653-8488 Ext: 230