[Rod of Many Wands (Complete Mage 128, 27,000 gp) Allows the firing of up to three wands simultaneously as a standard action, at the cost of extra charges.
That's wrong. Activating it is a full-round action.
Might I propose Nolzur's Pigments (DMG 263, 4,000 gp).
No in-combat usage whatsoever, but items that are -to a certain degree- only limited by your immagination are great.
I can't come up with anything better than a pit for ambushes or a portal to circumvent dungeon terrain, but I'm sure there are plenty of things it could be useful for.
Also, Robe of Useful Items is a favourite of mine (DMG, 266, 7,000 gp).
I think it's cheap regarding the possible situations where one of those patches might be useful.
Not to mention that you could actually
gain money if you rolled well enough.
Bag of Tricks, Gray (DMG 248, 900 gp)
Trapfinders. Or food, if you're starving.