>Hosting does not count: It's a physical asset.
If, instead of 'subscription business' you mean "businesses that rent access to software without much by way of per-user physical infrastructure" then yeah, I think some people would agree with you. I would. businesses think that because they have a low marginal cost per user, they think they can rest on those high margins. This might be what you are talking about, and if so, I agree. I mean, if you have a business with margins that are very high, investors notice, and they start trying to horn in on your market; either investors are willing to throw gobs of cash at re-writing all your software then saturating the market with marketing, or maybe someone open-sources something that can do a lot of what you can do, and suddenly you have a bunch of small competitors using the open-source software willing to compete with you at a more reasonable margin.
I was thrown off by your use of apple's hardware business as an example; I mean, selling intellectual property divorced from infrastructure is a hard problem, really, it's a different problem from the subscription vs. one time payment business models.