I don't buy that claim at all. No way you're building private infrastructure for 1/5 the cost of Azure or AWS. Or even 1/2.
If you're comparing some servers in a 4th tier colo with a poor SLA to AWS and pretending that devops time is free, then sure. But if you're actually building something with comparable reliability and availability, then no way. You're going to spend a lot more than you'd expect on extra capacity, a team of service engineers, load balancers, multiple locations, etc.
If you're comparing some servers in a 4th tier colo with a poor SLA to AWS and pretending that devops time is free, then sure. But if you're actually building something with comparable reliability and availability, then no way. You're going to spend a lot more than you'd expect on extra capacity, a team of service engineers, load balancers, multiple locations, etc.