The first mass produced color picturebook was published around 1900. I do not know what it was, but that is when it was possible. And by “mass produced” I mean a few thousand copies. The technology required two separate press runs (one B&W, one color– actually the color required three separate passes) and hand “tipping in” (gluing the color plates into the book.) It was reasonably expensive, per copy.
Given that copyright protection extends in the US to any book produced in 1923 or after, a significant proportion (75% or more?) of all picturebooks ever produced are copyright protected.
Now, over that time, most picturebooks went through a single (or perhaps a few) print runs of a few thousand copies. So, in any particular year there were a few books from the previous few years on bookseller’s shelves, and a new picuturebook had a modicum of a chance to sell it’s few thousand.
Fast forward to today. Children’s book publishers, who for the most part own the digital rights to that huge backlog of picturebooks, have figured out how to churn them into “digital” picturebooks. Now, once digitized, the marginal cost of producing a copy is zero. So today, someone wanting to create and publish a “digital” picturebook, unlike in the past where they were only competing against the few remainder books from the previous years, are potentially competing against ALMOST EVERY PICTUREBOOK EVER MADE.
This is a tremendous difference, and that is why I shouted it out in caps.
So, in economic terms, the supply of digital picturebooks is effectively infinite. That is to say that there are literally tens of thousands of “titles” each one with a marginal cost of zero. (This is as close to infinite supply as there has ever been in a commodity market I suspect.)
Now, let’s look at demand. Although population has increased worldwide, with ebbs and flows, we have roughly the same number of children of picturebook consuming age. Certainly not any order of magnitude more than at any recent time. So, demand can be said to be constant within a factor of less than 10.
So, we have more or less infinite supply and more or less constant demand. I suspect that drives the price to zero. And that is what we are seeing. I have tried to buck the trend, but I now believe that it is futile.
[Addendum (Oct. 25) It is worse than I thought, because we are not yet competing against every picturebook. I just checked the Caldecott Medal winners from 1978-2014 (37 years). Only 14 are available as iBooks. (Interestingly, 13 of the rest are available as audiobooks. A picturebook as audiobook seems silly!) So, even though less than half of the best picturebooks of the past 37 years are currently available digitally, we are still awash in competition.]