Yeah, you are. The assumption is you wouldn't try to sell an e-book for $102 (it says this explicitly) and you wouldn't try to sell fertilizer on the e-book advertisement (it doesn't say this, but it is common sense.). It is also assumed that we aren't making a shoddy product, nor something earth shattering.

The article is suggesting you use adwords demand compared to your expected optimal product price to determine if that market is over or under served.