One big problem with that is the dichotomy between "cloud" and "open source" - people will pay for SaaS but they absolutely balk at paying for licenses.
In this hypothetical scenario the real money might be in consultancy. "Sure, we can get your organisation set up with OpenNotAWSBecauseTrademarks. Our rates are $20K/consultant/week and we expect to bring a team of 5 for a fortnight." It just has to be a comparable cost and financial structure to how a large organisation trying to escape from cloud lock-in would have otherwise expected to engage their cloud architecture consultants or cloud security red team or other cloud specialists and then you're in the game.
Technology is a good business because a small labor input can scale to a very large impact. I'm sure there is a place for consultancy but I don't see it winning against "scale" in the long term.
Licenses are a major PITA when you want to be spinning machines up and down all the time. Some enterprise vendors have pay as you go solutions, but many don’t.
I get the impression that some enterprise vendors don’t offer pay as you go solutions because it would put their sales staff out of work, and because they wouldn’t be able to use a “how much can you afford?” pricing model.