The people we work with generally don't have $1000 up front and one of their main draws in publishing with us is that they have no other way of getting art/music. For those who have art already we shift that fixed cost towards promotion. Don't forget that we also offer code-level support to a lot of our devs and do extra stuff for them like optimize their OpenGraph actions. It ends up being a really good deal.

I should also point out that by using the SDK you can make three games in the time it would have taken you to make one. The Ghost template game was built and pushed to the App Store in the span of a few days.