> Their biggest benefit is to defer the initial setup of a self-managed cluster
And that, I think, is why (nearly) every startup, or indeed every new project, should begin on a public cloud. The capital waste of an incorrect server purchase can ruin a project and makes "fast failure" hard to stomach.
I don't move services away until an alternative is clearly both cheaper in 3yr NPV, and will not constrain future business opportunities. Except in cash cow operations where innovation has ceased, I rate the second criteria more important than the first and a compelling reason to stay on a public cloud.