In Breaking Bad, Walt had the opportunity to work with Gale and earn 3 million dollars. Instead he insisted on working with Jesse and split the money with him. He claimed it was because he didn't have chemistry with Gale but that seems like an unlikely excuse. What are the other reasons that Walt would give up 1.5 million in order to work with Jesse?
I think Walt knows that he is valuable enough to Gus until the point where Gus can replace him. And Walt also knows that once Gale masters the cook that Walt and Jesse produce, Walt is no longer useful.
Walt also knows that Jesse won't give him up, and that while Jesse is a good cook, he's not on par with Walt. This makes it almost a no-brainer for Walt to refuse to work with Gale, because the only 2 outcomes of that partnership are that Walt will be out of business or killed by Gus.
At the time, Walt wanted Jesse to drop charges against Hank, after Skyler had asked him to spare the family the pain of the pending charges. Initially, Jesse refuses the offer to join the "partnership", but moments later, Jesse calls Walt from his hospital bed agreeing to join the partnership. Also remember that during the time that Walt was excluding Jesse from his job with Gus, Jesse threatened to continue his production, even though he knew the DEA was aware of his connections to the meth. He said that he had a "get out of jail free card", which he explained meant that he could always implicate Walt to get a deal in the event he was caught.