The CK does several substantial things for Bethesda. Lets look at it purely froma business stand point. The Creation Kit requires upfront money to create/code/program. This takes cash from them, and in the short run they will lose out. Lets look at the long run though, a financing point of view. This down payment will create a lifecycle for this piece of software(skyrim) that will last longer than most of its competitors because its providing the customers a means of staying with the game, a continous means of staying with the game. Bethesda, with this Creation Kit is producing long term customers. Sure you may already have the game, "Thats right! How are they making money off me?". Its simple, advertising. You are promoting and showing mods off to your friends, this creates interest. You are also staying in the loop on the game longer, thus your paying attention to events and upcoming products for your software, DLC and such. Your staying with the game longer than it was intended not because of replayability but because you have easy access to content for free. I personally bought Oblivion purely becaus of the mods out for it. I bought it 4-5 years after its release. Bethesda makes a great deal of continous profit because of this. This is why the Creation Kit is such a good idea.