Let's see. Beast Shape IV is a level 6 spell, so CL 11 for a wizard. The duration is counted in minutes (cost multiplier 2) and it's supposed to be used only once per day (divide cost by 5). Makes 6*11*2,000*2/5, so I agree to the 26,400.
I think the price is steep - the spell will last only 11 minutes, that's just one or two encounters usually. And polymorph has its unique drawbacks. On the other hand, it can be a battle winner on lower levels which would justify the price.
There are multiple arguments for restricting it to one shape (or probably two): It justifies reducing the price (by ~30% for one shape, similiar to alignment restrictions), adds flavor, makes player's choice easier (no flipping through the books for 'best' option) and saves the GM some trouble with unexpected power spikes.
@SheepishEidolon: 6*11*2,000*2/5 = 52,800 not 26,400. You are mixing up price and cost.
1/day items are not continuous, so they don't get the *2 multiplier.
The equation is Price = 6 (SL) * 11 (CL) * 1,800 (Command Word) / 5 = 23,760 GP. Craft for half is 11,880.
The fun part comes in the material component. While zero cost, you still need it. So you need 50 each of every form you want to change into. Most people ignore this part.
/cevah
Yeah, 30% off sounds about right.
Most items that grant access to just one form typically have other abilities to compensate (and probably end up being more expensive than the guidelines).
Price reduction is for limiting who can use it, as that makes the item less attractive in the group. Making an item that only changes to one shape to lower cost isn't grounds for a reduction. The shape is going to be be fully taken advantage of when used, it isn't a drawback. It is attempting to use the pricing guidelines to get the effect cheaper than it "normally" would be available. Which is why they are guidelines and have examples of how they don't work often.