https://stackexchange.com/performance
Your average site wouldn't get anywhere near the same performance as them.
1. Almost all websites can run on a single dedicated server.
2. This is true for even something as big as Stackexchange which most sites are not.
3. If your site is indeed smaller than SE then that server is likely to be a few hundred dollars a month.
Also: getting a 512GB RAM server for 5-700 USD or so is definitely possible these days. But, again, most sites won't need anywhere near that. Based not only on information and belief ;) but first hand experience I sincerely doubt most sites would need more than 64GB.
What used to be a 30+ day procurement process became <7 days with VMs, became < 15 minutes with docker/kubernetes.
You can also do things that you would have never even considered doing prior to Docker - like run the application stack in the cloud, but launch one of the components (still in the same deployment) - on your laptop using tools like https://github.com/telepresenceio/telepresence.