Why are self help books usually shorter than novels and cost significantly more money?

I don't usually buy short self help books cause if I am going to pay a premium price for a book I want to know all the important details and I don't believe 200 pages is enough to summarize the most important points of the topic in a detail high enough to give you functional capacity in the topic you are reading about.

Why are self help books usually shorter than novels and cost significantly more money?
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