> On the other hand, if you use Kinesis, Lambdas, RDS, VPC peering, and IAM accross all of them including EC2 and EKS, then no, none of those other options can even come close. Purely the lack of system-wide IAM alone would be a dealbreaker.
I use AWS, but I suspect I'm a fair bit older than you.
Those things you say "you can't come close" - they exist elsewhere. There are just software libraries. It's the reverse of "can't come close" - there is a plethora of implementations to choose from, and most are free. Lambdas is just CGI on steroids, RDS is just a database, IAM is just one of any number of authentication / authorisation platforms the most notable one being kerberos which is literally decades old.
It's true that AWS's versions of these libraries all play nicely together, whereas the others are going to require more glue. But on the other hand AWS nickel and dimes you on every use. The price of writing the glue can be high and has to be incurred up front, whereas the price of the nickel and dimes - that's a future self problem. Just like smoking and crack. Not unsurprisingly the cloud vendors use the same tricks as the smoking and crack vendors too - they give away their delights for free to early users by handing out free credits like candy, knowing once you're locked in as a heavy user there is no way to avoid paying the piper.
The price difference in my experience is typically of the order of an an extra 0. That's not a big deal with your primary costs aren't CPU cycles but rather developer time. That's absolutely the case at the start of an enterprises life, and it seems to remain true for many enterprises for their entire existence. So perhaps AWS works out for many.
But personally, I would not take it for my business. There are lots of implementations of all the things you mention, and much more besides out there. Worse, many of AWS's products seem to exist to solve problems created by using other AWS products. Need to monitor you SES reputation? Don't record it yourself - send it to CloudWatch! It's only a small cost. Oh you need to get it to CloudWatch - use SNS - it's only a small cost. Oh you want to trigger stuff from CloudWatch - just use Lambda - it's only a small cost. Oh, you need to control access to all those things - use IAM. Maybe it's true it's all only a small cost - but it a very complex solution compared to parsing you SMTP server logs and writing them to a open source database, which is all that is happening under the hood. At times it seems the only reason AWS structures things in the way they do is to induce you into buying more AWS services.
Which is why things like TerraForm exist. Some are happier to where the cost incur the expense of gluing together the many free alternatives out there, in return for the ability to roll it out to the lowest cost provider out there.