[The Big D]

Originally Posted by James81

No, I'm talking about the situation that you have fabricated.

You even used the word "unexpected" to describe it and offered examples such as "car repair" and "medical."

You need to re-read what I actually posted, because I've already talked about the fact that exact same conflict exists even if the expenses in question are not planned. To make sure you don't miss it:

Originally Posted by myself

However, no matter how much you save, you can never alleviate the issue raised by 2). So there is always a tradeoff between the desire for planned personal expenses and the desire for planned family expenses. If you manage this tradeoff by means of separate accounting, you create exactly the same inefficiencies I described in my example when lower priority personal expenses edge out higher priority family expenses, or vice versa. Only this time they can't be alleviated by savings since savings must be retained for unplanned expenses [and no, you can't have arbitrary amounts of "extra" savings for planned expenses without violating 2)].