Avaliable for trade via steam =/= buyable with CE
Also Operation Crimson Hammer Expansion Mission Pack is NOT DLC.
Also making Expansion Missions buyable with CE wont make it free Expansion Missions. You know, for that CE that every player have in game SOMEONE had to pay real money sometime.
Making a Expansion Missions a CE sink, by making it buyable for CE ONLY from vendor would make players spent CE and thanks to that it would increase CE demand so more people would be more eager to buy CE with real money. OOO still profits.
Operation Crimson Hammer Expansion pack could work similar to shadow key (since OCH is basicaly a SL but with gremlins). It could work in same way, you buy item via CE (that will be untradeable and activated upon purchase) similar to key and poof you unlock OCH Expansion Missions.
But why OOO decided to make it buyable only with real $$$ .... and TRADEABLE via steam? Mystery.
(some say they are working on making Expansion Mission Pack tradeable via official client..... rumors? something to keep players from rioting? who knows...)
"Although the price to buy is $0.10"
Ha ha, try like $5.95, buddy. Still, it's pretty cheap, and I wouldn't be in Three Rings interest to change the price into CE form and essentially change it from cheap DLC to free DLC. If you and/or your parents can't afford to pay for OPTIONAL CONTENT, then that's your problem, not theirs.
Either wait until you're old enough to get your own credit card, or figure something out with your parents. Making the game even more free is not going to happen anytime soon, and if anything would cause the in-game economy to downturn even more. Besides, people currently are trading energy for the DLC via Steam's trading system (which you could say is a pseudo black market), albeit for much higher and appropriate prices.