I don’t get it though. What’s the payoff, marginally better comfort and typing speed or is it like having collectibles to own and show off? Personally, sure a mechanical keyboard is a little more satisfying to type on but who really cares.
As for the very expensive, mostly standard layout keyboards... it's an expensive hobby with marginal improvements at best, but the same could be said about furniture purchases. Most people don't choose furniture based solely off its functional characteristics. They want something pleasant to look at, especially since it's something they're using every day for a long period of time. I think there's plenty of utility in that, though personally I would never pay the prices that these people do.
[1] https://www.reddit.com/r/ErgoMechKeyboards/
DIY can lower the price, but it is a hustle and in the time needed is not free.
Maybe at some point Logitech will offer a split one for a more reasonable price, but I won’t hold my breath.