So what's with the masks being hawked on Facebook? Scam?

If I were you I’d hold out for a live monkey or a submarine.

Bait and switch scams are really, really common on Facebook and other social media ads - I’ve only really had in-depth experience of the phenomenon with tech products, but any type of product where there is a high quality version is probably prone to this.
The scammers steal images, ad copy and video from real products (usually high value and desirable quality), hack it around to remove conspicuous branding, spin up a quick shopify store and sell it at what appears to be absurdly low prices.
What they actually send will sometimes be a very cheap, inferior product of the same general type (so they can claim it was an honest mistake), or sometimes they just dropship any cheap product like a pair of sunglasses or a keychain, in order to get tracking info for a despatched item, which tricks PayPal or the credit card company into thinking the transaction is legit and enables the scammer to withdraw your payment and disappear with it.

The monkeys advertised in comic books were freaking real. They’d send you a live squirrel monkey. It was insane. Google it.

IIRC they were “sea monkeys,” which is a name for a type of brine shrimp.

That’s a separate thing. There was a time you could order real, live monkeys (and alligators among other wildlife) from those ads.

This. don’t buy anything from Facebook.

Yep. Google squirrel monkey comic book. There are some horror stories regarding them.

There were also real monkeys. I ordered sea monkeys, but wasn’t disappointed when they were brine shrimp. I’d read in a Jacques Costeau book about them, so I was kind of excited about it.

I Googled. Here’s one such story. It’s on the NPR website, so it should be accessible by anyone. And it’s kind of hilarious but also very, very sad. And there were other, similar stories in the search results.

Whatever you do, make sure you take it off right away if a Silver Shamrock ad comes on the TV.