French 6th generation fighter

[Ainen]

I'm not totally sold that a reduced size stealth aircraft will be all that much cheaper.

There's no particular reason it won't be. Stealth aircraft don't have a separate price curve, what they have is a similar development cost firewall.
But when passed, you use it the way you need.

I mean, people are buying Su57-sized airframes, and those are 75,000lbs/34tonnes. (Frankly, SCAF/Fr6gen's two named missions make it sound like it will look an awful lot like a Su-57.)

In most cases, either for a lack of better (competitive) option, or for a cool factor.
Flanker in many ways broke the market.