Ellevers,
My $1 commission is all in with the extra exchange fees that are charged with SPX. I think you all are right that it is not worth the cost. I am just amazed that someone would sell a butterfly for zero. These are spreads that are filled in the COB as spreads too. It is hard to resist a spread for zero, even if it doesn't make sense with commissions.
Many years ago when I was a floor trader in the OEX, another trader who needed to have a certain amount of trading volume for regulatory reasons, offered me a way out of the money put vertical for zero. He had 5,000 to sell. My commissions at the time were about .30, so this would have cost about $3000. I decided it wasn't worth it and passed. A friend who stood next to me ended up buying the whole thing. The next day the market collapsed and he sold the whole thing out for .50 netting $250,000. The spread went up to about 2 after that and ended up expiring worthless. I have never forgotten that. That's why its so hard to pass up any zero priced spread for me.
Ended up putting it on 20 times only today, just in case.