And yes, I think that price gap can be justified entirely by the insulation, when I look at energy costs per square meter in old buildings, available to me thanks to European requirement for energy performance certification. And that's even before PV so cheap it pays for itself in a year, which I have on my driveway right now.
The childhood home had single glazing, limited loft insulation, the cavity wall was just a cavity and had no insulation filling it, gas central heating. It was cold even with the heat on in winter.
So, I effectively spent just as much overall as my parents did, wage adjusted, but I'm much warmer for it.
Basically, I've gone from a childhood in a relatively big place that today would be considered "in need of modernisation" even at its best if it were listed for sale today, to a place which is about average size but of a quality far in excess of what anyone would have bothered to attempt for a normal family home when I was a kid, not even in a show home.
(And this was the cheapest new build I could find).