What are words worth?

I am a big fan of Amazon. And I often peruse their Kindle Singles just to see what is out there. For those of you who don’t know singles are $.99 E-stories. The main thing I notice is a variation of size of these stories. Some are 10 page short stories and others are 1000 page epics. Some sell like hot cakes and others people couldn’t give away with a hug. I can’t seem to track much in the way of rhyme or reason, so I figured I would ask the audience and see what everyone other there in social media land thinks. If there is one thing I learned from 7th grade science it was that there can only be one variable in an experiment. So, my question is how much would you pay for a 30 page E-story?