We're looking at two ways to handle this.
1. Integrate with the official Cost of Goods (https://metorik.com/go/cogs) plugin.
2. Allow you to set the cost of goods in Metorik itself.
And then offer reports taking into consideration the cost of goods, so you can see actual gross profit right in Metorik.
We are leaning more towards option 1, since it would significantly reduce the work required to integrate it into Metorik (as we wouldn't need to add the ability to set the cost of goods in Metorik), and it's less work for most users who already have it set up, since the cost of goods for each item is already defined.
Taking into account the cost of shipping would be good too, especially with the cost of 'free shipping'.