So, by your own admission, both of our answers make no sense.
Ha. You're putting words in my mouth. An overpriced item is not unbalanced - it's just not as desirable. A very, very underpriced item, on the other hand, actually unbalances the game.
The Book came out before the flashy spellbook extras from MaoF. It was the only Core spellbook that's waterproof.
You can hide your BBB in a Glove of Storing. Can't do that with a Library.
It's stylish, like having a palm-sized mobile phone when everyone else is lugging bricks.
Sure, none of that is all that exciting. You're splashing out. You don't
need it... but if you have it, you prize it... like you don't
need a sports car, but you take a lot of pride in having one.
Whereas ignoring scribing costs, on the other hand, makes it something no sane mid-high level wizard would be without. It's not "highly prized", it's standard issue. It comes with the pointy hat and the starry robe as part of the uniform. For 9k, you don't think twice about it.
I guess I'll be waiting for 3.5e to fix this one.
They're changing scribing in 3.5, so anything could happen.
-Hyp.