It doesn’t have to cost that. You probably can hire people remotely. E.g. Almost nobody in the EU will cost you that much. Most good devs are less than €100k total cost.
Well then we should just keep moving Eastwards from California until we find the cheapest teams we can and outsource to those, right? Let me know how that works out.
Plus if you are US based communicating in real time with Europe is a pain. And many EU countries have strict labor laws that limit working hours. Managers don’t want to have to get up at 6am just to meet their reports.