I believe it's possible to get a fixed rate "jumbo" loan for even more than that, but since they're "non-conforming" they can't be sold to fanny/freddy, and so the banks take on the full risk of these loans. For conforming loans, the limit in most areas is $647k [1], which has risen substantially in recent years (along with broader housing cost inflation). Not adjusting for HCOL areas would effectively be blocking lower income people from moving into these (arguably) "higher-mobility" areas.

[1] https://www.fhfa.gov/mobile/Pages/public-affairs-detail.aspx...