Well in my state you can add electricity and natural gas to the list. National parks also have additional fees (and privately-owned, price-segmented lodgings and restaurants) despite being a commons already subsidized by taxes.

Anyway, the point is not about the precedent but whether it is sensible. And that's not to imply that I love the country being sold off to billionaires and corporations right now. For medical care I go the other direction - we need the government funded base offering.