If you've ever seen or used one, that would probably be an IBM keyboard from the 1980s. Very heavy, loud, space bar doesn't break (but they fry the keyboard port if you hot-plug them). Using one is kind of magical, it's like you never press a key by mistake.
Examples are the IBM PC keyboard, the IBM AT keyboard and the keyboard used with the IBM PS/2 PCs. I think the keyboard cost several hundreds $$$ back then.
I wouldn't mind using such a monster (well, this one is still compatible with a modern PC, but it's missing the F11 key at least. F12 is kind of useless, I can live without lol)
Theses ones were very common, still thrown away 10-15 years ago (people or businesses throw all the useless computer trash together), I should have stocked up on them as they're not especially rare but quite sought after
If anything the modern ones are cheaper, as you can find some well under 100 $/€/£
I'd love to have a try at the new stuff, as the old stuff is really too clickety and loud. I played networked doom 2 (serial cable) on that thing and it was kind of a mess. Epic Pinball was fun, on the shift keys.