I reckon that for 99% of bikes sold it’s all moot anyway. There’s a tiny percentage of riders for whom such specific manufacturing would be noticeable.
Big tyres on road bikes are the next big thing, whether we like it or not.
I do, fwiw.
My new road bike will have 26 inch wheels so I can run bigger tyres without overlap.
There’s a big shift away from ‘racers’ to practical bikes too, which means mudguards, further eating away at clearance.
That means that pretty much everyone under, say five foot six will be on a frame which is compromised in it’s ability to effectively handle the overall wheel diameter with bigger volume tyres.
But as I’ve said, it won’t happen.
All the designers I’ve ever heard or read discuss proportional sizing say the core business lies in the middle ground.
As to cost.
With frames, I know Surly, Thorn and Spa for example practice proportional sizing with respect to tubing and in some cases fork as well as frame geometry.
Their frames don’t seem to be anymore expensive than less thoughtfully designed competitors.