I have done the maths lots of times and by the time you add up all of the support costs as well as the initial investment and setup, it is rarely, in my opinion

I have done the maths lots of times and by the time you add up all of the support costs as well as the initial investment and setup, it is rarely, in my opinion, worth it for a small business to even consider doing anything other than renting platform as a service (or SaaS if they can). I ran a cloud platform production system for 6 years with multiple replicas of all systems and it cost around £400/month, a tiny amount compared to even a single person to manage your own servers.