Well, mainly because I had no idea about the actual costs. I kinda spoke too soon.

I just thought that moving that much data would cost some serious money. Apparently that's not really moving "that much data".

Wrong assumptions on my part :/

The engineer time to reimplement the other AWS services you're using may be substantially more than the $54k difference in bandwidth costs.

Depends on what they're using AWS for. OP seems to be running a simple and straightforward setup that just happens to use a lot of bandwidth. It doesn't take five full-time engineers to maintain a handful of LEMP servers.

Nothing prevents you from mixing and matching there are actually AWS services you can't find cheaper equivalents to elsewhere. My experience is that those of my consulting clients that want to migrate off AWS rarely have any problems replacing it. The cost savings usually pay back any development costs and the overall migration effort in 2-3 months at most.

If there will be 2 such companies, for that 108k I can wrote services backend that will be comptabile with AWS, so after a year you can transparently switch to that system on your bare metal and sell it to have your services for free.

I still didn't make my own "clone", because I can't afford machines to start selling it.

Hmm very unlikely. Thats 5 full time people.

More like 2 or 3 if you include overheads. Depends on location, of course.

It's where they make their money. Like when a restaurant pushes the desserts on you - the desserts have the highest markup by far on the menu.

AWS has a lot of 'free' services, which still have to be paid for. Some of those free services are things that benefit both the client and AWS, but would be avoided by many if folks had to pay for them (like IAM credentialling)