“It's cheaper on AWS” really depends on where you're starting from, too. If you actually need more than, say, a bare Linux box it's usually hard to even start collecting the staff time + costs for the equivalent enterprise environment with network infrastructure, monitoring, access management and audit logging, the various fault-tolerance / recovery options, etc.

It requires care to do a comparison which actually measures the subset of features which you use — I've seen the other side of that where someone justified dropping a ton of cash on a particular option based on a specific feature but, jumping ahead a few years, never ended up using that due to performance/stability/security issues.