The 10% overhead is largely advertising and a way to get preorders (after you are established)

But, while software (gaming), take a look at some interviews with Larian and Obsidian/inExile (I forget which one of those... probably both). They keep returning to the KS for fundraising and a large part of it is that even a successful campaign and perfect release doesn't necessarily give them the capital to start the next project without investors.

Personally: I backed the first pebble KS and got an okay product (looked like crap and not a lot of utility, but what it did, it did well). But I definitely got turned off by the multiple campaign thing (and the frequency of them) as it suggested a lack of long term support for the product.