More info: https://github.com/pcarrier/planck
With the current figures (~10 kits), the entire kit (PCB, top, and bottom) will be sold for $59, but could get down to ~$45 if quantities increase.
Right now, the PCB has a spot for a Teensy 2.0, but we may be designing a board with those capabilities built-in (for around the same price).
The firmware will support any configuration you desire. Examples:
Pierre's Classic: http://www.keyboard-layout-editor.com/#/layouts/46aa7b0762cb7a535eaaf1e49644398f
Jack's: http://www.keyboard-layout-editor.com/#/layouts/313d2d43c1b86c7d223aa7ced2a67102
Pierre's Ergolemak: http://www.keyboard-layout-editor.com/#/layouts/6404f1346108887c37f781da0dc0e6c7
An interactive example: http://thumbs.club/