So it appears that one of the companies I’d have been competing with, Readability, have thrown in the towel.
Robojar (my effort) has a similar but distinguishable model. And others have tried and failed in this space with similar-but-distinguishable models.
Nobody as yet has cracked the right permutation of small adjustments to the micropayment concept to make it work. I believe that I have the secret ingredients, but based on historical evidence I have every chance of being wrong.
I look forward to finding out.