I think the original source is on a youtube channel: https://www.youtube.com/watch?v=QPKKQnijnsM . The video aggregates data from multiple sources:
http://www.motherjones.com/politics/2011/02/income-inequalit... http://danariely.com/2010/09/30/wealth-inequality/ http://thinkprogress.org/economy/2011/10/03/334156/top-five-... http://money.cnn.com/2012/04/19/news/economy/ceo-pay/index.h...
How reliable these sources are, I'm not sure. If the information is wrong, I wouldn't blame it on Upworthy, it's a distribution channel after all.
Furthermore, 'true' captalism with a truly free market is quite unrealistic, since it would require all participants to be effectively omniscient and infinitely rational (and even then you would have to compare it to 'true' communism, where no one is ever selfish or lazy)