I wrote my thoughts just above. Mike didn't kill him because it never would have worked out for Nacho. The cartel would get to him. This way, Nacho is in a position to continue to make mike money, rather than the one off 50 grand. kaylee aint going to no state school.

Mike is not toeing any line. He went long beyond return when he took out his son's killers. But frankly he was probably already there after a career as a dirty cop and an apparent sniper in vietnam. Mike is what he is. but now he has motivation to push forward to make that kaylee money.

Mike chose not to shoot Tuco because Mike depends on repeat business. Mike needs that money, more than 50 thousand. Nacho could be his new meal ticket if Nacho is in a stable power position. Oddly, Mike came to this reasoning just before Ellsworth actually said it out loud to him regarding his own business. But thats…