If we set up a dog-eat-dog world where only money matters, why would a billionaire hoard unneeded masks? They know that they can just buy what they need when the need it. The only people with incentive to hoard are poor and vulnerable people because they know they won't be able to afford masks when they run out. Entrepreneurial types looking for arbitrage will probably cause weird things to happen in the short term, but after a month or two things will rebound sharply to whatever the new normal is going to look like.
If this crisis has taught me anything, it was a mistake not to hoard. I assumed I would be able to buy what I needed at outrageous prices, instead I ran the risk of running out of toilet paper because prices stayed unreasonably low.
If bankrupting hoarders with high prices is going to be unacceptable, I'm going to become a hoarder out of necessity next time I see a crisis inbound. I'll stock up on much more toilet paper than I need because I can't predict when governments/major supermarkets/public at large will let me buy the stuff at market price; which is clearly a bit higher than what the supermarkets are charging.