He probably won't make anymore from this fight than he would from a Brook fight. But the difference is that the Brook fight will always be there for him. By fighting Canelo first, he can fight Brook later, and make twice as much cash in the process. It's a smart business move.
Sure, but this isn't like Mayweather, where you got HUGE money and, at worst, got a boxing lesson. Here, you get big money, but not Mayweather money, and get KTFO. Khan truly believes he can win, I have no doubt.