Determining Costs

[Aseroth_Blackward]

I'm in the process of setting up a campaign, and I have some items of my own design and/or converted from pathfinder that I want to add. The only real problem I am having is trying to figure out an accurate way to determine cost. Has anyone put out some data or numbers on how the book prices were developed? Or knows of some similar threat that can help me crunch the numbers?