I don't doubt the conclusion, but I think we would be buying (life expectancy - age) life years instead of 1 life.
I like geeking out over masks and there are a lot of options. I have a bunch of models, and if you'd like to come try them sometime (next EA Boston meetup on 10/26?) I'd be happy to show you what they're like.
I think it would be great if you can gather some data about how many people prefer which of the options and publish it.
That's an interesting recommendation. I'm unfamiliar with buying reusable masks, do you know a good way to decide whether to buy a small, medium or large mask?
A pandemic that's substantially worse than COVID-19 is a serious possibility. If one happens, having a good mask could save your life. A high quality reusable mask is only $30 to $60, and I think it's well worth it to buy one for yourself. Worth it enough that I think you should order one now if you don't have one already.
But if you're not convinced, let's do some rough estimation.
COVID-19 killed about 0.2% of people (20M of 8B). The 1918 flu killed more like 2.5% (50M of 2B). Estimating from two data points is fraught, but this gives you perhaps a 0.02% annual chance of dying in a pandemic. Engineering could make this much worse, especially given progress in AI, but let's set that aside for now to make a more conservative case.
A reusable mask ("elastomeric respirator") would be really valuable to have, if things got really bad. Let's imagine they cut your risk of dying by half: the rated efficacy is much higher (99%+) but real-world use isn't perfect, especially over the months or years another pandemic could last.
A mask should last at least ten years if unused, and over that decade it would drop this conservative estimate of your risk of pandemic-induced death from 0.2% to 0.1%. If you, as the US DoT does, value not dying at $14M, then this is worth $14k. Even if the benefit of a mask is 100x lower than we estimated ($140), it's still worth it to buy one.
I like geeking out over masks and there are a lot of options. I have a bunch of models, and if you'd like to come try them sometime (next EA Boston meetup on 10/26?) I'd be happy to show you what they're like. But if you just want to pick one and be done with it, leaving it in a box that you more likely than not don't need to open, a time tested but somewhat garish option is the 3M 6200 mask in Small ($17), Medium ($15), Large ($19) plus a set of 3M 2091 p100 filters ($7/pair):
I'd also recommend buying one now instead of trying to notice when a pandemic is coming: buying now ensures you get one instead of scrambling when everyone else is competing over a supply that can't keep up, and everyone who prepares ahead of time helps reduce shortages when a disaster comes.