eamon
Explorer
It's only somewhat too expensive. Ring of Wizardry (IV) is 100k, and that's 6 pearls of power. At that point, the extra versatility might definitely balance the two spell slots - esp. since you can do both ;-).
Comparing it with the version for spontaneous casters; which is 24k at that level, the ring is clearly better than the pearls. It doesn't require a standard action to activate (which might come at an unfortunate time), and it doubles your spell slots, which, if you're a sorcerer, means up to 6 extra spell slots, whereas the pearl-like items only prove 4 at that price.
Of course, at the level you'd be then, there are probably better items for that price anyhow.
Comparing it with the version for spontaneous casters; which is 24k at that level, the ring is clearly better than the pearls. It doesn't require a standard action to activate (which might come at an unfortunate time), and it doubles your spell slots, which, if you're a sorcerer, means up to 6 extra spell slots, whereas the pearl-like items only prove 4 at that price.
Of course, at the level you'd be then, there are probably better items for that price anyhow.