Hello Scott
If you set your system to use Weighted Average (In Store Operations Manager, File --> Configuration --> Inventory) and your Purchase Orders to update supplier cost (File --> Configuration --> Options --> Purchase Order options), you can have proper COGS.
Let's say you received 6 items at a 5.00 cost, and sold 4, so you now have 2 on hand. Your inventory is 2 x 5.00 = 10.00
You order in 6 more, but the cost has increased to 5.20. On the PO, you receive the six and change the price to 5.20. When you post, you will now show 8 items on hand, and it will have calculated the weighted average cost as ((2 x 5.00) + (6 x 5.20))/8, or 5.15
In items, the General tab will now show 5.15 as your cost, but your vendor cost will show as 5.20 (the last price - check your Inventory tab)
If you need to report on current cost instead of weighted cost, you could always modify some reports to use the SupplierList.Cost instead of the Item.Cost