Remember when Apple started charging Amazon and other eBook competitors a 30% royalty fee for selling books in their eReader apps? It turns out that it was a direct jab at Amazon. And the idea stemmed from a commercial that showed how easy it is to switch from an iPhone to an Android phone.

As part of the proposed antitrust remedy to the case against Apple (the one in which Apple was already found guilty), the US Department of Justice has filed a revised proposal, which brings new documentation to light. In a 2010 email exchange between Steve Jobs and Philip Schiller, we can see where Jobs got the idea to take 30% on all eBooks sold through apps. Schiller complained to Jobs about an Amazon Kindle app commercial showing how easy it is to switch from an iPhone to an Android phone. Jobs responded by writing:

What do you recommend we do?

The first step might be to say they must use our payment system for everything, including books (triggered by the newspapers and magazines). If they want to compare us to Android, let’s force them to use our far superior payment system. Thoughts?

The DOJ is arguing that this email proves that Apple lawyers were misleading the court with earlier claims that Apple takes a 30 percent commission from all retailers for all goods sold through apps. The court points out that a consumer could buy a pair of shoes from Zappos, for instance, and does not earn a 30 percent cut on the deal. (Via 9to5mac).