The medium board does not breakout the 2x18 header to any terminals, just the 2 side-of-the-board rows.
Assembled prices are $52, $36, $30, plus shipping & paypal fee, if that's what you're asking.
The 12x15 grid is prototype area for a user to wire up some extra circuitry. I'm not aware that anyone uses it, but it's there if needed.