More info on the "Pittsburgh Professional Athlete Fee", which is paid by any nonresident who uses public facilities to perform:

The City Code, Title II, Article X, Chapter 271 imposes a usage fee equal to three percent (3%) of earned income upon each non-resident who uses a publicly funded facility to engage in an athletic event or otherwise render a performance for which a non-resident receives remuneration. The usage fee is a percentage of the individual’s income attributable to such individual’s usage of the facility.
A copy of the ordinance:
http://apps.pittsburghpa.gov/finance...ports_regs.pdf