> no one wants to tell their boss they want to disable RDS HA and wear 1h of downtime a year so they can cut 50% of their spend.

If you're a SaaS, 1h of downtime costs a lot of money. In reputation, in lost business, in support time, in on-call response, in making a public postmortem and sharing it to customers and dealing with responses... For saving a few thousand bucks, it's often indeed a very bad deal.