Is saving 50% also a worthwhile goal at expense of being on prem, and all the downsides? Asking honestly because that’s where my business is in terms of the decision. We won’t save 90% but we will save 45-55%.
Still, I think it's hard to justify going anti-cloud in an effort to cut costs. Without a very skilled and experienced team doing the migration, the end result is very likely to be some hybrid setup that's the worst of both worlds. Especially if you're using a managed service, the open source alternatives might not be the drop in replacement that they claim to be.