Ordering that amount of amount of servers takes about one hour with hetzner. If you truly want a complete rack on your own maybe a few days as they have to do it manually.
Most companies don‘t need to scale up full racks in seconds. Heck, even weeks would be ok for most of them to get new hardware delivered. The cloud planted the lie into everyone‘s head that most companies dont have predictable and stable load.
Most businesses could probably know server needs 6-12 months out. There's a small number of businesses in the world that actually need dynamic scaling.
rental period is a month
you can also use hetzner cloud, which is still roughly 10x less expensive then aws and that does not take into account the vastly cheaper traffic
Most companies don‘t need to scale up full racks in seconds. Heck, even weeks would be ok for most of them to get new hardware delivered. The cloud planted the lie into everyone‘s head that most companies dont have predictable and stable load.