These days you can get solid mechanical switch keyboards in the $60 to $100 range. The only downside is that they all seem to come with LED backlighting and obnoxious gamer marketing, but once you turn off the light shows they're perfectly good keyboards. I think they would qualify for "Model T" status.
They have mechanical switches but often lack N-key rollover (I think the blog post gets this wrong) and instead have a watered down form marketed as "anti-ghosting". But that's more than enough for all purposes except maybe Emacs olympics and social prestige with keyboard-philes.
I bought a Filco Majestouch 2 three years ago when I finally had to retire my 8 year old Sidewinder X4, which was a $40 membrane keyboard with deeper-than-usual key travel. I can definitely say moving from that to the Majestouch 2 has not made me a better programmer, typist, or gamer. And it hasn't helped with ergonomics either. It just feels better the same way shelling out the extra couple hundred bucks for a high end graphics card makes games feel better.
I owned an actually ergonomic split-key keyboard as well (Goldtouch) when I developed RSI-related wrist problems as a teenager and kept it around for 15 years. That keyboard made an actual difference and I would take it out of the closet whenever my wrists started acting up even from the Majestouch 2. But you don't usually see ergonomics front and center in super expensive mechanical keyboards - because IMO in that price range and in that community it hasn't been about practical concerns for a while. And that's fine - I'm not going to judge someone's choice of things to collect - but I see no practical benefit to spending substantially more on mechanical keyboards.