Frame damage is actually pretty straightforward on cars that actually have a frame (i.e. aren't unibody).
The problem with repair costs in modern cars is all the sensors, cameras, complex paint jobs, airbags, etc. Those expenses add up quickly, combined with the added costs of body panels
and trim for certain brands and costs really get insane - it shouldn't be a surprise that car insurance costs keep growing much faster than inflation.
Definitely depends on the type of damage. Cracks and rust aren't a big deal at all, a twisted frame due to a corner collision is a royal pain.
In the context of price to repair though, I'd still rather be dealing with a car with a damaged frame rather than a modern car with loads of sensors, body panels, etc that all need replacing.
I think most of the time if you are in a serious enough accident to damage the gigacast in a way that it needs replacing, that would've totalled most other cars as well.