The board that spans the roboRIO to reach the screw holes comes to about 3" x 3". We were going to use oshpark.com again as we have had good results from them in the past. They charge $5/sq in for 3 copies, which comes to about $15 per board. Add header pins, and it's not much more than that, depending on how you buy.
The board could be made narrower - we were sticking with the footprint of our other board.
My only issue is that for a passive board with only breakout pins, there is a lot of empty space.
The mini version is a total of around 6sq in, so about $30 for 3. So I guess security costs about $5 per board.

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FRC Team 111 - WildStang (Mentor, Drive Coach)
FTC Team 7458 - Full Force! (Mentor, Coach)
FRC Team 3132 - Australia's FIRST FRC Team! (Holy crazy first year, Batman!)