So $MEGACORP abuses their absolute monopolistic position in the market to underhandedly negotiate with book publishers and force their hand into working the way $MEGACORP wants: in order to gain access to $MEGACORPs completely dominated (but technically not a monopoly*) audience who wishes to buy books in a convenient way online, book publishers must bow down to $MEGACORP and pay the tax. Meanwhile, everyone else who sells books through alternative avenues is decimated because the audience only wants to buy books through $MEGACORP.
And you can replace $MEGACORP with both 'Apple' and 'Amazon', and it is 100% factually accurate. Beautiful. It's fucking turtles eating turtles all the way down.