Real people don't behave like this. A billionaire can't make personal use of a million masks and there is no point in stockpiling them during a crisis just in case there is some future crisis. They're not going to be worth more a year from now than they are today because by then either demand will be lower or production will be higher.
So nobody would be buying a million masks to hoard in a bunker right now. The people buying them would be the people who intend to use them.
Then you need to differentiate who needs them the most, but there is no way to do that efficiently from the top of a tower. And willingness to pay is a pretty good proxy when marginal utility falls off pretty quickly with quantity. A software engineer isn't going to pay a high price for a thousand masks they don't need any more than the billionaire is going to buy a million. But a doctor's office might very well pay a high price for a thousand masks they do need, which is exactly what you want to see because it causes them to get what they need.