Creating a variable priced item with fixed margins

I have created an item with 0 cost and 0 sale price with a 10% margin and adjustable price. The idea is to record items not in the system with a  generic product title (MISC_NON_SCAN_ITEMS)  with a set margin of 10%. Eg. I select the "MISC_NON_SCAN_ITEMS"  adjust the price to $2 and save. I expect the profit report to record $0.2 for the sale, but it comes up with 100% margin of $2. Any ideas on how to make this work?