The economist in me agrees with you but where is she going to live? Just going to ship her out to West Virginia?

I'd be OK w/it if you have a humane way to implement it but I doubt voters in the city would ever sign off on it.

Well, that's kind of the point - if the possibility to live in a particular place is scarce and so desirable that it costs $4000/month, then you either can afford that or don't live in that place - and this mechanism is useful; it allows people who really value living in that particular spot to pay the premium and do so; and the money flowing in provides a strong incentive to increase supply.

If Grandma needs subsidized housing, that is something that should be separately agreed upon and implemented, presumably from tax revenue. The idea of forcing landlords to pay that subsidy basically at random seems ridiculous to me, the kind of thing that results in discrimination and legal fights.

Part of the problem with talking about some policies is differing visibilities of suffering. Yes, the old grandma who has lived in the same apartment for 50 years has very visible suffering if you make her apartment market rate. However, what about the people who were never able to move to NY to start their career and family because of the policy? Or a family that had to leave the city and everyone they knew because they couldn't afford it, and the grandma monopolized all of the 'affordable housing' benefit?

To me, that's like saying grandma doesn't deserve to keep $2 million house she bought many years ago for $20 thousand because someone with $2 million wants her property.

How much sympathy should we have for Grandma McMoneybags here when people making in situations just like hers are helping drive a housing crisis?

In California, this isn't a hypothetical. Especially because she pays property taxes as if the thing is worth a number much closer to $20k than $20mil.

Why so? Here Grandma owns the house, but in the other situation she doesn't own the apartment, the landlord does.

Because the landlord knew exactly what they were doing when they rented the apartment to Grandma. If the landlord didn't want to enter into a contract the involving rent control, they shouldn't have been in the business of renting NYC apartments.

Contract law usually doesn't allow for lifetime contracts because people can't consider such a long timespan logically. Rent control is the same thing. It forces a contract with on going payments and services with no end date. Is there any escape clause?

As far as I'm aware, people occupying rent controlled apartments (in NYC) can opt to be bought out by their landlord. I've heard a number of stories of people using that windfall (generally buyouts are on the order of $10^4-10^5) to improve their general living situation, and I've also heard stories (including someone I knew personally) of people squandering that windfall and ending up living out of their car.

IANAL...

I believe the landlord is bound by the language of the law, not the contract. If the law enabling grandma's rent control were fully repealed, there'd be no rent control-related reason the landlord couldn't raise Grandma's rent to market rent. Basically, Grandma AND the landlord both needed to know what they were getting in to.

Grandma: "I want this apartment."

Landlord: "OK, it's $250/month with rent control. But just so you know, if they ever repeal that law, and market rate is more than the $250/month you're paying, I'm raising you rent."

Grandma: "Understood. If I were the landlord, I'd raise the rent on the grandma renting my apartment, too."

Isn't a sale a lifetime contract?

Apartment rental is explicitly not a sale. We should probably keep talking about the same thing and not keep moving the goalposts to suit our argument.

Isn't an NDA a lifetime contract?

I have never seen (and certainly have never signed) an NDA that covers an indefinite period of time.

Not true: blanket legislation in NY brought all buildings constructed pre 1947 into rent control and rent-stabilization to pre-1974 buildings:

https://ag.ny.gov/sites/default/files/tenants_rights.pdf

And to people who view "sale" and "rent" as interchangeable, that might make some sense. A better argument might have been to go the property tax route but that's still not very convincing.