This really puts things in to perspective. Subscription startups looking to get some percentage of the population to pay $10 a month can never reach the scale of google advertising when they are extracting nearly that much value on average from every single person.
Well that's part of the problem inherent with the subscription model, isn't it?
Google can make >$100 a click for ads on mortgages or insurance keywords, but subscription models are locked in to revenue that doesn't scale with the category of use - unless they become some sort of affiliate service.