You sum it up very neatly. We've heard this from quite a few companies, and that's kind of why we started our ours.

We figured, "Okay, if we can do this well, reliably, and de-risk it; then we can offer that as a service and just split the difference on the cost savings"

(plus we include engineering time proportional to cluster size, and also do the migration on our own dime as part of the de-risking)