"Bring your own tools" is not exactly novel in the workplace. Maybe so for office workers, but not more generally. Anyway, these particular tools are cheap enough that it hardly even matters who is expected to pay for them.
The $20 a month tier in particular is a trivial expense, on par with businesses that expect their workers to wear steel toed shoes. Some may give workers a little stipend to buy those boots, some not. Either way, it doesn't really matter.
Just because it's not novel, doesn't mean it's right. I also don't agree with, for example, many mechanics being forced to buy their own tools (especially what little they get paid).
I don't do tech outside of 9-5, so either my employer pays for it all, or I don't use it. Simple as that. Thankfully, they do pay for it, but I couldn't imagine working somewhere that says "You need to use AI" and then not providing it on their dime.
Quite frankly it should be regulation that if a W2 employee needs something to perform their job duties, the employer must provide it.