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Ways to think about market size. — Benedict Evans

That is, its easier to predict 'cheaper and better' than to predict the changes in behavior that will come from that. And pricing is only one dynamic - once the price falls below a certain level it stops mattering. Cheaper and better is necessary but insufficient: if billions of people can afford it, it doesnt follow that billions of people will buy it. You need to have a theory as to why more and more people will care.