What you say about Airbnb vs. hotel costs in NYC is wildly not my experience. At the high end, the rooms available on Airbnb simply aren't available in hotels at all; I'd wager, if you did your best at apples-apples, Airbnb is roughly half as expensive as a hotel room.
The nondeterminism thing with Abnb is a good point. I've always figured that if something fell through, I'd just book a same-night hotel, but it was a concern.
Two NYC-area Abnb rentals, off the top of my head:
* A 4-bedroom 2-storey attached (townhouse-style) house in W'burg, less than a block from the Bedford stop; full kitchen, back yard(!). Cost less than any 3-star pair of adjoining bedrooms we could find --- and we booked 2 months in advance.
* A full-kitchen king bed studio in Chelsea, for ~150/night.
The last one is from a few months ago, the other from last year.
By the way: both of these feel like textbook cases of the kind of situation where Abnb is a win for everyone involved. The owner of the house was picky about us, checked in on us while we were there, and was renting a whole building to one party. The Chelsea apartment was its occupant's primary residence; they were renting it out while themselves traveling.
I think it's the situations where people are literally running full-time businesses on top of Abnb where we start to run into trouble.
The nondeterminism thing with Abnb is a good point. I've always figured that if something fell through, I'd just book a same-night hotel, but it was a concern.