Contracting is more akin to mining for (high) pay. A better simile would be something like RubyMotion (http://rubymotion.com) by my friend Laurent Sansonetti. That's selling pickaxes (and excellent ones at that). Training for iOS developers would qualify as well.

When you build other people's apps you are still digging for gold, you just get paid to do it, hence eliminating the risks (and the gains too, if the App becomes popular). But what I think meant with this simile is that instead of being an app developer you can be a service provider to app developers. In his case, he became a consultant, in my case, I develop APIs and other server-side code for App developer, and sometimes also manage the whole setting up of servers for them. My guess is that after the first wave of success, many people without software development background joined the gold rush and only focused on learning how to write apps and later they found out there is more to it than that.

I assume he is referring to Apple making tons of money selling app developers the tools they need to make apps. Iphones, macs, developer licenses, etc.