Try doing the math and ask why your time costs. You need to buy a lot of storage to pay for the engineering work and most places would prefer to spend that time and attention on the product rather than shaving a few percent off of the storage bill (especially since the savings will be negative for quite some time).
Wait, I'm confused, are you arguing for or against S3? Did you mean factoring the time needed to obtain the multiple PhD levels of information in tracking the cost, usage, and security of those interoperable services plugged into S3?
Many of us just don't buy your argument. "Engineering work" for maintaining our own storage is not rocket science.
You just plug it in and basically it runs. Thats pretty much it.
Having to explain to an HN audience how installing an SSD is trivial is weird.
I have done the math as part of my job and often found that yes, it was literally worth the money to do our own storage in cases. Running a highly available, durable storage system is not particularly difficult. There was an era when it was a common skill for a sysadmin. In the current era there are off the shelf solutions for it, both open and proprietary.
The biggest reason people pay for S3 is because of data transfer cost to other cloud services they are using.