> that of course you can hack something together in a weekend that does this. However a analysing a million edge cases, making sure all failures fail in a safe way takes a lot of time and knowledge.

Thats true for a lot of things. Most developers can whip up a Slack clone in a weekend, create an uber clone in a weekend or create a Netflix clone in a weekend. But dealing with all the edge cases, the details, making it scalable, etc. that's were the pain is.