I can't find the source now but I have a dim recollection of a breakdown of stuff that ate in to the final number for a another kickstarter (possibly Wasteland 2) that had 10% went in Kickstarter/Amazon fees, about 1% went in unfulfilled payments and various other amounts to physical goods etc...
Damn, wish I knew where I saw it. Thought it was in the Q&A summary thread...