But it's already unaffordable for the average NYer before it's even ready. If wealthy foreigners can park their money in manhattan, they will, without living there. That doesn't help scarcity for actual residents.
I don't see why that's an argument against. If they are going to plow their money into a city it's better if it's into 1 or 2 units in a dense skyscraper rather than buying entire mid and low rise buildings. Residential skyscrapers are strictly better at reducing price pressures.
I'd have no problem at all with those billionaire towers but for the nonsensical property tax breaks (421a, J51, etc). Throw in a small non-resident property tax differential and I become an enthusiastic booster.
If a bunch of billionaires want to pay property taxes while using barely any city services that sounds like a win to me. We can use that money to provide better services to the people that do live in the city year round.
In my observation the people who are most bitter about billionaires "buying up Manhattan" are the multimillionaires who want to be on the top of the heap.