The tradeoff is that quality of life is terrible. The cities are full of petty bug people. And COL makes living standards precarious for all but the wealthy and the extremely poor (government programs). The precariousness also inhibits the formation of stable IRL (as opposed to chat group based) friend groups.
That said, after half a decade of this I've saved enough money to go back home and use stocks, real estate, and side hustles to put down roots with a decent quality of life.
Sometimes I feel like Odysseus on Ogygia. It's easy to be trapped in one of these hubs so long that you miss out on the chance to exit young-adulthood gracefully. (Very sad the number of friends I have who decided to start a family too late and couldn't quite make it work out).