I don't know where the person in question is, but those numbers seems low if you assume zero hours of maintenance for the cloud setup, sure.
The thing is, you're not likely to spend amortised more than minutes a year maintaining the on-prem hardware (or you could rent managed servers and spend nothing on it), and as they pointed out they already spend hours maintaing the EC2 instance.
I wouldn't typically recommend on prem hardware for just a single server - if you already have a rack and a proper setup, sure - otherwise just rent a cheap server somewhere, and ensure you have backups.
The thing is, you're not likely to spend amortised more than minutes a year maintaining the on-prem hardware (or you could rent managed servers and spend nothing on it), and as they pointed out they already spend hours maintaing the EC2 instance.
I wouldn't typically recommend on prem hardware for just a single server - if you already have a rack and a proper setup, sure - otherwise just rent a cheap server somewhere, and ensure you have backups.