I think they will go for something like ( price_of_the_book)/(no_of_pages) for a single page. So it should not be a problem though.

Historically I think, may be, some of the 19 century books like Charles Dickens The Great Expectation may suffer from the problem you mention. These books used to be published like periodicals like a single chapter would be released each week(like soap). It made sense to lengthen them for financial benefit.

I am not sure, kind of anecdotal, but I think lot of people don't read or finish lot of books.

That should be adjusting by itself though, since lower density of content lowers the want to continue reading.