I analyzed some projects in progress once (http://creativepark.net/1381) and that number is about right. There is some variability based on the financial scope of projects but not as much as I expected.

The main issue in my opinion is that Kickstarter tricks "ordinary" people into thinking they have a decent chance of getting funded. In reality of course only socially well-connected projects have a good chance.

In 2011, Kickstarter reported its overall project success rate as 44%: http://www.kickstarter.com/blog/shortening-the-maximum-proje...