I have a friend who studied the Toyota Prius gearbox at university to try and figure out improvements, I can say for a fact that their drivetrain is trick as fuck. So in some sense it's reasonable for them to charge a higher price and profit from their R&D work.

Like I say though, I’m sure they stretch the pricing well beyond what is reasonable.

It's definitely something of a gimmick, like 3D TV, and especially in its early iterations. However you did just list a genuine benefit of hybrid technology. Also, I know someone with a Mercedes hybrid and that will go up to like 50 mph on battery only, and also delivers ridiculous acceleration like that I've only previously felt on motorbikes, all the while keeping fuel economy above 90 mpg and never bothering to plug it in. The only real downside is how much space the batteries take up in the boot.