Well it's more like you'll get the usable parts without a huge premium. The was a time when monitors faster than 60hz were premium but now it's pretty common to see 120hz and beyond on even basic monitors.

There's still diminishing returns as you go higher, but there's definitely a noticeable difference between 60hz and 120hz, as well as a less noticeable but noticeable difference between 120hz and 240hz.240hz is becoming more standard now on regular high end monitors and beginning to trickle down too.

Beyond that in terms of response times, you might not notice a difference between 240hz and 360hz, but image clarity will be better because you'll get less ghosting just from the virtue of the pixels changing so quickly, so it's not entirely useless.

Part of the reason you're seeing this is because they can. The panel technology (OLED in this case) is super fast due to it's design, so it's not too costly to add the necessary hardware to drive those speeds. For LCD tech, you do get to drive the panels faster and harder, that's why older screens required shitty TN panels to get those refresh rates, but everything else has been around for a while.