So in the module, you're told of the Coward's Pearl. However, you're not told how it works, or what it does exactly. Thankfully in the Q&A, they tell what it is and what it does, but they don't give specifics. Doing the math after realizing what it did exactly, I came up with the price, etc. However, after using Google, I found out that someone wrote it up a bit better than I initially would have.
When activated, this bracelet fills a 20 foot radius spread with 20 foot high clouds, as per obscuring mist, and transfers the user to another location within 680 feet, as per dimension door. This bracelet is usable once.
Moderate conjuration; CL 7th; Craft Wondrous Item, dimension door, obscuring mist; Price 1,450 gp.