In addition to their newsletter, their website has some useful goodies like an etsy fee calculator. Just plug in the price of an item you sell, the shipping, the actual postage, and the cost of materials and this handy-dandy little tool will spit back out the profit that you will make on this item. There is also one for ebay and one for Amazon.
I highly recommend this site. And, no, I don't get anything out of recommending it other than the satisfaction of knowing that I have provided some useful information.