So there's a "Square Enix" sale on the PS Store right now. The bundle containing the base game and Heavensward is there for $20, and the base game is there for $10. Heavensward alone is not on sale, and is still $30.

Except if you already own the base game, it will not let you purchase the bundle at all, and you must buy Heavensward separately. I don't know whose fault this is, but great job.