Yeah ego, that's all. When I turned sixty I thought, I have the money, why not have a real nice cue?
So I bought a Schon with ivory ferrule, diamonds and such. It's very pretty. 
Last week I played the best pool of my life against a much, much better player.  With close pool playing friends as witnesses too.  I was using my $200 McDermott sneaky pete. I though about that Schon and the other cues scattered about my basement.  What a sap. Lesson learned. If I ever spent 5 or 10 G's on a ivory encrusted Black Boar carved by the elves of the Black Forest, I'd shoot myself. 
Now I understand the "investment" argument that you tell your wife. And if this is what you want to spend your money on for fun or collecting, fine. But please, get real about how it helps your game.