with such a big pile and walt not exactly knowing the total, he knows they were going to take some.
but saul thinks about leverage and insurance and it isn’t ecessarily for him to take thge money, but to KNOW where it is in case he needs a bargaining chip with walt, lydia, todd’s guys, and/or the dea.
I actually take Saul as being honest with his clients. He is a co-conspirator, after all.