Armstrap: Open ARM development board
armstrap.org
armstrap.org
Complete with datasheets and Gerber files: https://github.com/armstrap/armstrap_eagle/tree/master/1.0.0...
https://www.olimex.com/Products/OLinuXino/A20/A20-OLinuXino-...
The current STM32F4 Discovery board is less than $25, including 8M of SDRAM and an LCD display.
If you want an open source, free to resell, free to remix or change (with access to the CAD designs files), multiplatform, easy to hand solder, cheap to replicate in large quantities board, then an Armstrap Eagle is a better choice.
It looks like the Armstrap Eagle is a bit more expensive than those corporate boards but you'll probably be in a better position to ship your kickstarter ontime if you started with an open board from day one.