AWS isn't going to help you setup your security, you have to do it yourself. Previously a sysadmin would do this, now it's the devs. They aren't going to monitor your database performance. Previously a sysadmin would do this, now it's the devs. They aren't going to setup your networking. Previously a sysadmin would do this, ...
Managing hardware and updating hosts is maybe 10% of the work of a sysadmin. You can't buy much on 1/10th of a sysadmins salary, and even the things you can, the quality and response time are generally going to be shit compared to someone who cares about your company (been there).
