Obviously, you don't play golf. Scratch that. Obviously, you've never been to Singapore.
I have very fond memories of walking out of the air-conditioned shopping mall above the Waterfront MRT station and then walking through Mount Faber Park, Henderson Waves, Southern Ridges Park, Kent Ridge Park, and then back into an air-conditioned shopping mall at Kent Ridge MRT.
I took one of those walks almost every day, and in many cases co-workers or friends decided to join, because with the MRT system it's just so easy to quickly zip over to nature in your lunch break.
It's difficult to access this objectively, but I'm 100% convinced that this was a major factor in making my time in Singapore some of the most productive months I've ever had.
Also in Italy, the town squares were usually full with families and the elderly, sipping coffee and reading newspapers. But it was well understood that just by being there, they signal that they're available for you to just talk to people. Again, I felt like the strong communal spirit of having talked to 100+ neighbors in your village was fantastic, even if you only did small-talk about the newspaper.
Now if you could reduce the depression rate and related issues by 10% with a new well-maintained park. That'd be a significant GDP boost, so the economic value of such parks is probably in the billions of $$$.