I fail to see the equivalence. I'm not contracting with Anvil for development or support. I'm basically buying a tool, in this case a tool that is more expensive than my hosting costs.
One, if you're using it commercially, it's going to pay for itself pretty quickly. I rarely do client projects for less than several thousand pounds; I reckon I could probably churn a lot of them out using this in half the time.
Two if you're not using it commercially, it's still a very low cost; maybe more than pure hosting but it does a lot more than just hosting.
Honest question, this looks awesome but how would a contractor justify using it? Would you somehow swallow the risk of them going out of business for whatever reason and promise a rewrite for clients (is that something you can get insured for?) or would clients just be okay with the risk? It seems like you'd have to have already bought enterprise to be able to run this without them from what I can tell?