Examples:

If you are a mortgage broker or a car dealer then 1000 clicks is easily worth $2000. Even if only a tiny fraction of them leads to a sale, each sale is worth thousands of dollars.

If you are Prada or Lexus and you need people to associate your brand with high-value objects like iPhones, then even high CPM's are a good investment; especially because high CPM's price out the rabble, so your fancy brand won't appear next to an ad for psychics or penis enlargers.