Wacom lowered the price of the Companion. I agree that originally it was overpriced, but now I think it's fair, which is why I bought the 256Gb model. It's the same price as a SPro 3. And before I ramble about the Companion, I agree with your assessment of the SPro 3 over the iPad.
Anyways, with the Companion it not only has support for tilt, but rotation via the Art Pen, 2048 levels pressure, and no need for batteries. There's also the option for of other pens, like the mentioned Art Pen -- which I bought; and each new stylus has its own unique ID, so in programs like Painter each one can be a completely different art-tool. The Companion also has programmable thumb buttons, which are really useful.
And for programs like Painter, tilt is absolutely essential and the same goes for rotation with some brushes. But I guess that depends on one's art style and preference of tools.
For my own needs, the Companion was worth every penny. It's more than met my needs and completely replaced my MacBook Pro + Cintiq 12wx. If it had not been made available though, I would have bought a Surface Pro.