I agree the Quest is a good deal at $399 (I paid $299, the original price) but is something still a good deal if it's no longer used and on a shelf with similar dusty inert equipment?
Well, it's certainly a better deal than paying $3,000 for the same result?
What I'm trying to say is that Apple introducing such an expensive unit will make people take another look at the Quest as an option to see what the XR fuss is about. $400 is impulse buy territory for a lot of people who might be willing to try out the technology, while $3k isn't.
If the result is “sitting on a shelf unused”, yes, both $3000 and $400 devices are equally capable of that. (As my own history of excited gadget purchases bears testimony…)
The point was, if you’re unsure whether you actually would keep using it, the Quest is a much cheaper way to scratch that VR/XR urge.