Well, you have a natural experiment right here. N95 masks were out of stock from the beginning, while KN95 never were, and prices were higher, but still affordable for the vast majority of the time since the beginning of the pandemic. It varies between suppliers, but I (in an eastern european country) bought my parents a box-of-boxes of high quality masks when I found a decent price. I think it was about $200, and there's still enough left for a couple of years. Still no shortage.