So, first: taking the granted skill of a headband of vast intellect and making it switchable when preparing spells. I was lazy and just slapped a 50% increase to the enhancement bonus; seems reasonable, not terribly spendy. My own thought is that the switchability should be restricted to a single granted skill, regardless of the enhancement bonus and/or presence of multiple skills.
Thoughts on the price structure? Does anybody have string feelings about it being too cheap? I do think it's a very useful ability, granted. I'm working to push the trope envelope about wizards doing everybody elses' job. Combine the switchable skill with fabricate, and become a successful merchant: create your stock after checking the market. Sell wholesale to local merchants if you don't want to deal with customers; you're still making bank.