He's trying to eliminate ideas for products, not sell an existing one. I.e. if he writes an e-book, is the cost of sales going to make it a net loss, if so, he should make a product at a higher price point or pick a different niche.
Adwords is appealing since it's an auction, and they let you see some of their data. In your example of using SEO instead, you have to do the SEO work with either your time or someone else's, so it's not like the cost is zero.
Adwords is appealing since it's an auction, and they let you see some of their data. In your example of using SEO instead, you have to do the SEO work with either your time or someone else's, so it's not like the cost is zero.