There is only a certain period of time from which you can profit from any particular good. If you make a hamburger, you have probably 2 hours to sell it before it goes bad and is worthless.
And likewise, if you create a cell phone, you have maybe 2 years to sell it before nobody will want it. And if you make a movie, you have a few months where you can sell the movie (in a theater) and make money from it. Once the movie hits the internet the ability to make money off it decreases (piracy will happen more in the future, not less). Make a new app for the iPhone and you have a few months where you can make money before a free alternative arises.
This is technological deflation. And the pace is increasing. The time you're able to make money is decreasing rapidly. Mathematically, as that time approaches 0, the effective price of everything starts reaching $0. Why buy anything today, when it'll be effectively free tomorrow?