Are you having a laugh? 100k? For a AAA quality tech demo? That wouldn't even cover 1 guy for a year.
Mechanics... Art... Writing... VO... Audio... UI/UX... Codebase... R&D... QA... Iteration... Release...
You're looking at 3-8 million over 1-2 years, just to get started. And that's being frugal. The wide cost band there allowing for modern teams of either very high or low efficiency/talent.
If you wanted an indie-spec, something akin to the (still late and over budget) System Shock 1 Remake, you're still looking at at least 1-2m over 1-2 years.
I'm of course assuming you want something actually good. You can't just slap an FPS Controller in Unreal and some asset store art with a dialogue system and moody ambient music and call it a day lol.
The 100k figure in the quote was for an indie team, specifically on established and easy-to-use engines like Unity or Unreal
If we're talking indie team using Unity or Unreal, I dunno, probably 100k will reasonably do it
Indies range from one dude in his basement to massive teams who are basically AAA in all but name and publisher.
If an indie team needs 1-2 million and 1-2 years to build a
tech demo, they are utterly incompetent and a waste of money.
So... basically par for the course.