This is a spin off from a topic on Air France about the same AF flight LAX-CDG being $200 less if purchased as codeshare through Delta or KLM.
What are the financial transactions between the two airlines involved when a codeshare ticket is purchased?
Same question for what happens between the airlines when I use my Delta miles to purchase a flight on AF metal. Why would AF offer miles flights for Delta?

side question- If I work real hard, I can occasionally find a saver rate business ticket on AF LAX-CDG for Delta miles. Any way to get more access to such flights? I have only Ivory status on AF. Should I cross over to an AF miles card, if such a thing exists.