And what purchase price did you pay for High Sierra?
But you haven't. Your Mac came with Sierra, El Capitan, Yosemite, whatever.
Any kind of features they add to future macOS upgrades are subsidized through future Mac hardware sales, sure. But you don't miss out either way whether they add a feature or not.
Again, this would be entirely different if you bought a piece of hardware and Apple suddenly would announce it lacks a software feature. E.g., if they were to first advertise the iPhone X as having Face ID, then backpedaling and saying it'll receive it in a future update. I think that would be a more suitable analogy.
In this case, I just don't see how that fits. Should they have delayed High Sierra altogether instead?