On a single board that's pricey, but when I consider how much I spend on bespoke boards and keycaps, it comes pretty darn close to that. And there absolutely are mechanical keyboards in group buys that go for that much. The mechanical keyboard hobby, like most hobbies, can get super expensive.
Though that really is not something that is targeting gaming. Those boards look nothing like weird ASUS thing, but instead go for more more artsy, industrial looks.
As a random, recent example:
This went for 530 Euros,
Derivative R1 Keyboard Kit
(already sold out, since these are produced at very small numbers, which explains the price: you pay for the fact that it's very much not a mass market product)