Can you explain why?

They cannot, because they are wrong. And I say this as a person who has owned no small number of fancy cars (but I got better).

A new base-model Prius is absurdly luxurious compared to a base model car of 1975 or 1985 or even 1995. If you have lived long enough to see this change, then dropping 2x or 3x or 10x the cost of the Prius self-evidently puts you wildly beyond the point of diminishing returns.

The Prius is going to have excellent climate control, and a phenomenal stereo. It's going to have adaptive cruise control, and will warn you when you drift out of your lane, or if you're about to run into an obstacle.

Outside of motorsports-sorts of things, what you get out of more expensive vehicles is of limited utility. Mostly, it's just showing off.

Now, if you want a track weapon, then yeah, you DO get more by spending. But for a regular person who wants to get from point A to point B comfortably and safely? The Prius is fantastic, and it's hard to justify spending more unless you're willing to admit that it's a keeping-up-with-the-Joneses kind of thing.