My impression is the standard compute (as in CPUs+RAM) isn't expensive, it's the storage (1 PB is less than half a rack physically now, comparing with the yearly prices listed), and so if you don't have much data, the value of on-prem isn't there.
If you're a Windows shop, Bitlocker has been available to you since 2008.
If you're a Red Hat shop, Clevis + Tang has made this a no brainer since 2014.
If you have lots of money and run your root filesystems via FC or iSCSI from NetApp filers, then NSE has been around for close to 20 years now.
If your infrastructure consists of ten t2.micro instances vs ten Raspberry Pis, then sure. In any other case, migrating VM or bare metal workloads from your own hardware straight onto EC2 is one of the most effective ways in the world to incinerate money.
You can do well if you've got a workload well suited to 'native' PaaS services like S3 and Lambda, but EC2 costs a fortune.
For businesses with <10 servers and half an IT person, the cost difference is practically irrelevant. EC2+EBS+snapshots is a magic bullet abstraction for most scenarios. Bare metal is nice until parts of it start to fail on you.
I can teach someone from accounting how to restore the entire VM farm in an afternoon using the AWS web console. I've never seen an on prem setup where a similar feat is possible. There's always some weird arcane exceptions due to economic compromises that Amazon was not forced to make. When you can afford to build a fleet of data centers, you can provide a degree of standardization in product offering that is extraordinarily hard to beat. If your main goal is to chase customers and build products for them, this kind of stuff goes a long way.
Long term you should always seek total autonomy over your information technology, but you should be careful to not let that goal ruin the principal business that underlies everything.