Yup, you have to buy it for EVERY profile... if you have kids - like so many do that want to play - it's going to set you back about $300 all up.
It's a horrible setup for customers. Of all the games I play, ZoS are the only ones with this business model.
Watch how FDev do it with Elite Dangerous. You buy the base game and first expansion - all expansions that have followed have since be free so long as you purchased that first one. People spend TONS of money in their store for aesthetics and stuff. I don't think I've purchased a single aesthetic for ESO... because they already rip money from my hands rather than me giving it over.