You are quite right in your assumptions in that she had hers done at a Public Hospital whereas I opted to go to a Private Hospital. However, I got a quote from the Public Hospital where she was treated, and for the cataract removal and basic lens fitted they were going to charge me app 40,000 baht, whereas she paid 6,000 baht! I don't mind paying slightly more, but almost SEVEN times as much is a BIG price differential!!!
(I opted to go to a Private Hospital because (a) A couple of farang friends had been there and recommended it highly, and (b) the Public Hospital did not stock the type of lens that I required.)
Regarding your point re "parks, museums, monuments, etc., etc.", I wonder how Thais would feel if, for instance, they had to pay £50 to visit London Zoo, whereas the locals only had to pay £10? (Figures for illustration points only!)