0.2 Full-time employees to build all the automation, scale up (and down!) the stack as needed, monitor, operate and maintain it at an HA level? That is a huge feat, and I'd love to read about how you pulled it off. Please consider sharing your story, and perhaps your Salt recipes ;)

With all those things that you have in place, AWS would not be a big win for you, though you still might find some use of AWS services like S3 for reliable object storage, Route53 for DNS, or Lambda for "server-free" event handling. The unique thing about AWS is the huge portfolio of services they have and the absolutely amazing rate at which they manage to pump out new (and useful!) ones.

It takes some weeks to get it working, I'd say two to four, depending how often you've done it. Then for weeks there is nearly no Ops at all (security updates only mostly while the servers are humming) with releases done with Docker push by developers. Adding and provisioning a new VPS takes some seconds (and some seconds later checking), with Consul the stuff running on the VPS usually integrates itself). Sometimes hardware breaks down, then it's either setup a new VPS (setup_server <IP> <Role>) which takes around 5sec or mail the hoster if it's a DB server with a (mirrored RAID) SSD crash, which takes around 2h to fix all in all. So on average per year I'd guess 0,2 Ops FTE (which equals 10 weeks a year, which is a lot if you're not Facebook and don't need to do releases of new app versions). Today ops is relativly easy with a well trodden path, it's not 1999.

The Salt is of the shelf, with some bash scripts on top to auto generate some config and make installation of a new server one script call.

We surely could put endless hours into Ops, playing around with stuff etc. but the benefit would be marginal.

Our DNS setup is simple, not much to say, we use DNS Made Easy for failover, we use S3 though I do not consider it "AWS" (S3 is comparativly cheap).

I've wondered about Mesosphere with autoscaling etc. but with adding a new VPS in seconds setting up Mesosphere/Kubernetes taking two weeks would take quite some time to amortize.