I think the counterintuitive thing about bringing up Brazilian cities here is that central Sao Paolo (where just the central part has about 3x the population of San Francisco) feels richer than San Francisco. And the favelas on the edges, which have a population larger than the whole Bay Area, feel poorer than almost anywhere in the world, with nowhere in the US that can hold a candle to such. And just the favelas of Sao Paolo have a population larger than most US states.

Cities wax and wane. SF boomed from the gold rush, 1880s-1906, 1920s, 1940s, 60s, and as you noted, dot com period. In between it’s varied from stasis (1870s, 50s) to quite grim (30s, 80s — the latter much worse than today).

The swings in Silicon Valley and other parts of the Bay Area have been much less extreme in these regards. Most of the wealth is in the Valley, just more diffuse and harder to see.