Name one company that runs 4 servers of ruby and earns millions per year
Given that very few companies in the world make their infrastructure public and I never worked in a Ruby shop, I can't.
But I've done it with Python and I can't see why Ruby would be any different.
A company makes millions of dollars through 4 servers running python?
Yes, 2-4 web servers. And it's not like they are using most expensive configuration, just 4 vCPU per node. CPU utilization is below 20%, so it could even run on a single node, but that's not good for availability.
Why is that so surprising? Nobody sane does anything CPU-intensive in their webapps.
You can easily reach "scale" (earn millions of dollars, serve millions of customers) while still running on 2-4 web servers.