I must say that if scalability is not part of OSS then it inevitably smells fishy to me. I am willing to pay to avoid the pain of maintaining or designing clusters but not because it's the only way to scale up. There are too many options that allow to scale with OSS version now it's hard to justify it. It's still a no-go for me.

Again, just take it as one person's opinion. I can't even grasp how complicated and challenging is to run what you offer. This is strictly user's opinion.