Hello there, @danielkpurnell.
Thanks for visiting the Community. I appreciate the information you've shared. Yes, QuickBooks uses the average cost to determine the value of the item.
When you sell an item with insufficient quantity, your item cost will become your default average cost, and will be posted in your COGS account. Check out this article for more insights: Understand inventory assets and COGS tracking.
At the moment, there isn't a way to turn off the average costs in QuickBooks Desktop. You may want to upgrade to the Enterprise version so you can use the FIFO features instead so the inventory won't calculate using the average cost method.
Read through this article for more insights about the average costing and the FIFO method in QuickBooks Desktop: Average Costing vs FIFO. It also helps you learn about how each method analyzes inventory costs.
Feel free to message again if you have additional questions. We're always delighted to assist.
