I'm not sure it's really even enforced? For example

Republic of Tea blackberry sage tea, 50 count - $11 on their site, $13 on Amazon with Republic of Tea as the seller.

https://www.republicoftea.com/blackberry-sage-black/p/v00590...

https://www.amazon.com/dp/B0024SDYLI

And that's not really a super obscure product, since it's ranked #69 best selling for the "black tea" category.