It's an interesting question: whether attractions should charge an entry fee in order to dampen demand, and how much it should be. In my head, museums should never charge more than about $15 to enter; but that's probably horribly out of date.

#travel smh.com.au/traveller/reviews-a…

Yet another previously free attraction is now charging tourists

Many major cities’ best attractions used to be accessible for free. Now tourists are expected to stump up cash in order to see them.

^{Michael Gebicki (The Sydney Morning Herald)}