Just taking a quick look at several different retailers of trad gear, a single pair of Wooly Whispers (or most fur strip options) run from $5 – $6, and that’s before you’ve paid for shipping.
So, getting two pairs of Scallops for $12 (and free shipping) doesn’t seem any more “ridiculously expensive” than the other commercially-available options. And, when you factor in that they are easily re-usable (which most wool/yarn puffs aren’t after using them for a while) I would say they’re actually pretty cost-effective compared to the competition.
Of course, making your own silencers from scratch will always be cheapest, but you could probably buy a pair of felted wool soles and cut out enough scallops to last a lifetime (or go through the time-intensive process of felting your own wool…). Personally, I’m ok with kicking a couple extra $$ to a homegrown trad company of really nice folks who make good stuff.