Do you have numbers to back that up? Pre-COVID. Personal income tax numbers have increased until 2018 (last year I can find) which indicates that taxpayers were coming in rather than leaving.
- rising cost of living, propelled by foreign investment in housing, pricing out even upper middle class
- more taxes
- more crime, and less policing
- shitty schools
As soon as you don't need to be in the expensive city for work, it's like hmmm, why the hell am I putting up with this? People with kids may be slightly less flexible, but anybody young and single can basically move very easily. People forget that companies can move easily too.
In terms of amenities, city governments forget that the whole microbrewery/dispensary/expensive coffee shops/hot yoga/avocado toast ecosystem has basically been franchised out at this point and is trivial to stand up anywhere. Sure, it's not an opera house in Manaus, but lots of cheap places in the US have more culture than Bellevue or San Jose.
Expensive cities will argue people will return, and sure, some will, unless the city is too dangerous and completely broke from the tax base leaving. If you are young and single, and want to be around other young single people, and let's say a little midwest spot becomes hip and has the basics, and lots of people move there, you don't really need NYC (at least not everybody). And $500/month rent for a nice 1 bedroom (or a mortgage) is appealing.
You are aware that there are only two places in the world to have globally renowned theatre districts? NYC's Broadway and London's West End.
No periodic Osheaga can outdo music venues in Brooklyn.
There are things that stick. Things that would have to move. Things that seems "easily replicated", but are only possible in extremely densely populated areas.
PS: I just recently moved out of NYC to a town 1 hour north of NYC. And I hate NYC. And I still can see what is impossible without certain factors.
*Software Engineer in Bay area gets paid more, than in NYC.
Live performance is art, which is opposite of materialistic.
Smaller and more niche artists sell out medium sized venues in NYC, while failing to get half occupancy in fairly large cities. That is a major draw, because even idealistic artists need food.
I'm not speaking of just money and property, but rather, anything which pleases our lizard brain - this includes things like tourism, sex-for-pleasure, video games, and novels.
Some counter-examples that I don't consider materialistic are: personal relationships (family and friends), pursuit of justice, philosophy, and also creating art.
I suspect that an extremely awesome scene can be replicated anywhere there is suitable mass of interesting people who can live cheaply. Sure, it's not going to be top billing, but for 99% of us, we simply don't care. Having a hundred different live shows to go to any weekend is more than enough for us, with lots of great local artists.
New York is still way more affordable, than many other places(a busy bar bartender can get over $100K in tips). You also have to realize that outside of NYC you need to have 1 or 2 cars per household and you need way less space for stuff in your apartment in NYC(product and service availability make it easier to depend on things "being there")
Portland is an outdoorsy city, barely a cultural hub - it's cool in its own way. Its appeal is way narrower, than NYC.
Berlin is literally massive city with political power and financial prowess. It could become another global center, but like London - it's its own thing. Very different to NYC.
(speaking from personal experience here)
NYC was also kind of a bad example for me to use because actually, it's a really clean city. When I visited in 2016 I couldn't believe how much cleaner and safer it felt than my hometown (Portland Oregon).
I went to all areas, manhattan, brooklyn, the bronx, harlem, queens, and I just didn't see the sad human decay (Giuliani kicked them all out I guess).