But you couldn't, could you? 400 million is more than Hetzner total revenue.
I think 400 million is staggering amount of money to be used for computing, but if you are using that amount of money there are only handful amount of players that can absorb that kind of money and provide you services.
And deal with the physical stuff ( racking, cabling, cooling, electricity, DCs) and networking stuff ( high quality redundant networking routers, switches, firewalls, the engineers that can use them) ? It's quite possible it would cost more than $400 million / year to do all of that properly at a global scale, and a big part would be paid upfront.
I think you could have a server running for about every 10 or so users that are online at the same time.