I'd definitely call that the best explanation. You spend a few years working at a GAFAM, and now you've got a hugely prestigious resume from an expensive, high

I'd definitely call that the best explanation. You spend a few years working at a GAFAM, and now you've got a hugely prestigious resume from an expensive, high-cost-of-living area that other companies will shell out for, big time. You spend any time outside that cluster, even doing excellent and difficult work, and you just don't have the prestige. It's also a matter of scale: the GAFAMs just ship more units in terms of revenue per employee. Sure, that's largely because of monopoly and network effects, but hey.