That's not a fair assessment and I'm surprised this is the top comment. In this case, the huge advantage to a containerized setup is that everything is now easily portable. If his server goes down, or he just decides to move, OP can now deploy all of his websites onto another server instantly. He also quotes the ability to build (and test) locally before shipping images to production, which is a really neat workflow. Improved security comes as an added bonus.
As for the "s3 costs of docker image", it's a few cents per month.