Hi there, Liftco.
Thank you for taking the time to get help with setting a selling price for the items you sell within your company. I've got information about this.
The option that you're looking for is not available. QuickBooks will always use the Sales Price when selling an item instead of the Average Cost. You can, however, create a Price Rule for a specific customer representing the divisions and for the items you sell in those divisions.
First, go to your list of items and list all the items you sell within your company, and get the average cost.
Second, create a price rule for those items:
- From the Lists menu, select Price Rule List.
- Right-click within the table and choose New.
- Enter the name and the description of the price rule.
- Click the + icon to assign a customer.
- Set the date range.
- Click Price Overrides to assign a custom price to the items.
- Select OK.

You can create a sales transaction after creating a price rule. Here's an article for your additional reference: Set up and Use Advanced Pricing.
Let me know if you need help as you go through the steps. Take care and have a great weekend!