It affects a subset of sellers that send stuff to amazon to warehouse and ship for them. If you store and ship your items yourself then you dont get dinged.
Amd i think at least amazon is putting the increase only on the people that benefit the most from amazon doing deliveries for them.
They are already paying more anyways for warehouse fees. Most fba sellers are larger and are able to handle the increase better than smaller lower volume sellers not in the fba program.
They still have to be very careful about raising prices on some of their core users. Ebay was notorious for screwing over everyone, and their market cap has been doing pretty lousy from it