There is the cost of your service or product (your time, materials or costs), the fee or prices you would charge on the open market, and then there is the value you would put on it when trading for something you might never have had the luxury nor the budget for.

FORBES: Bartering for Survival - Have I Got A Deal for You

If you pushed on an open door in space, it would push you in the opposite direction.

CNN: Kepler or not, we'll find life in space

It would begin the year you open your first Roth and apply to all money added later.

CNN: Tax Cut For Savers

You look on all six sides and it would appear impossible to open.

FORBES: Japanese Secret Boxes: The Coolest Security Puzzles for Kids and Adults

Since you need to have the D415 open to do anything, the clear key would be more convenient on the slide out keypad where you will use it to erase mistakes.

ENGADGET: Phone Factor: The Samsung D415