He is getting away with it because he is not establishing a price. It is a bidding war. (I do NOT approve of it).
The State of Texas AG is going after a similar case now, but the seller is claiming he did not establish a price other than a $1 start.
What the dumb bidders don't have enough sense to think about is that they could get a good seamstress to make 10 with enough layers to make it N95 for $50. $75 max.
I know that charity auctions do this and thousands of dollars are paid for a $50 item in the name of charity. These guys are claiming similar. It may cause a revision of laws that deal with emergency situations with critical needs products.
I remember the oil shortage of 73-74. Most oil companies were selling gas at $0.25 to $0.30 when it struck. Nixon froze the gas prices to prevent gouging. But suddenly gas was selling at $.40 minimum. The oil company arguments were - the prices were at $.40 (40 cents) but we were giving rebates of variable amounts based on volume. Since the price was froze, they withdrew their "rebate" or what ever term they used, to the customer (service station owners) and the price was suddenly 40 cents a gallon minimum.