I've gotta figure that there's always the second situation, where the wizard on his own would be able to make use of his escape button spells with greater ease, while doing so with a fighter in the party could lead to his death, if you can't bring both of you for whatever reason. Wizards are often pretty good at that sort of thing.
Eh, the fighter can always sell what he can't use, and as the thesis of the thread states, he needs the money more.The wizard "ally," being a wizard, can use all of your gear. As you yourself noted, the wealth value at which more gear becomes redundant is likely extraordinarily high, so this guy stands to gain quite a lot of power if he can bump you off and take your stuff.
At some point, this starts to look a lot less like a party, and a lot more like a wizard and his flunky. In any case, there's always the reasonable possibility that the threat to the earth exceeds the value of any random item stack.The fighter has a lot less to gain even if he were to somehow be able to overpower you, which is also less likely to be successful - two corners of the fraud triangle (motive and opportunity) are much smaller for him.
Then there might not actually be a point where it works out that way in a game that follows WBL. It follows logic pretty well, actually. If more money can't make you more powerful, then there's something to be said for the idea that not much else can make you significantly more powerful either. It doesn't math out perfectly, but I think the window of this being the way to go is narrow enough that it's pretty irrelevant.Once you get to those levels wealth starts to become irrelevant anyway (as does class - you can simply Team Solars and there is no more "fighter") so the entire distinction breaks down. Though again, aside from a Tippy-style setting this won't happen in-universe anyway or it already would have.