Best way to get data for cost of goods report

I am not aware of a cost of goods report, maybe there is one and I am not going to have to do it?
I also have a major issue in that we are not actually selling the items.
We are removing inventory using physical inventory variance.
As I understand it I need a quantity on hand at the beginning of the period.
I think countProductInventoryOnHand will give me the count I need, but I will verify.
If that works I am hoping that will give me beginning inventory, and ending inventory.
My understanding it is (beginning + purchased) - ending. So I am curious how to get purchased.
I confirmed it is really received, so I could do a count of receiving records for the time frame?
Any one have experience with obtaining these sums, is there a sum view and a service already for receiving totals by product for a time frame?