Pay by Number of Pages Read
Why?
You receive value from consumption of the book.
How?
Have a mechanism for ebooks where you pay a much smaller fee when buying the book (maybe $3 of the total price of $10 for the book), then only micro-pay for pages you actually read in that book up to the whole price of the book.
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Pay to Comment
Why?
A revenue stream and to filter who can comment.
How?
Have a mechanism for people to comment online (on a blog post or an article) only if they pay a small amount.
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Rate Answers by Users Paying for Them
Why?
As a good measurement of what was the right answer.
How?
Allow users to donate how much they want (maybe even less than 1 dollar cent), based on their satisfaction of the result they got in the SERP. This will give a better indication as to what is a really useful answer to a specific query.
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