IF your ticket is non-refundable you will have to pay a change fee. The reason no airline would let you do what you're proposing (not show up for the first leg of a flight and just fly the second) is because it can be cheaper to book a round trip than a one-way and what you're proposing would get around that fare rule.

As another post said always check to see if two one-ways are cheaper than a round trip. If you had these flights as separate reservations you could just not fly one and still fly on the other. However, booking two one-ways can also come back to bite you - if you need to make a change to both flights you'd pay the $200 change fee for both.

Short answer is if your travel plans could change don't buy a non-refundable ticket.