There are 18.6 million millionaires in the US. If each of them bought 10 n95 masks just in case, or for themselves + family + friends, that's 186 million masks. They could easily pay $20 / mask (that's only $200 per millionaire), which would significantly push up the cost to hospitals of acquiring masks.
Hospitals might not even be able to afford the masks they need. They are having budget shortfalls due to the ban on elective surgery. Cuomo was complaining about paying $7/mask, and NY state is going to have budget shortfalls as well due to the recession.