There’s definitely a huge dichotomy between the $50-90/sqft costs you cite and what actually gets charged for rebuilds. Apparently, after last year’s fires in Santa Barbara, rebuilding cost $300/sqft. And that was true even when folks were only insured to $200/sqft.
The mortgage broker we used (who claims to own several rental properties, and probably has good contacts in the industry) told us he paid about $300, so it doesn’t seem to just have been the chumps.