Hello, doris14. 

When you set up an inventory item, the cost unit you entered will not usually change automatically. Once the cost constantly change, it will also affect your balance sheet and profit and loss. 

To check why the cost keep changing, I'd recommend reaching out to our Customer Care Team. They can do a screen sharing session and help you map and correct it.  

Here's how:

1. Click the Help icon located in the upper right-hand corner.
2. In the Help window, click the Contact Us button located at the bottom.
3. Enter your question and click Let's talk.
4. Choose either Start a chat or Call us.

If you have the new QuickBooks Assistant help update, you can follow these steps:

1. Go to the Help menu, and select Talk to a human.
2. Choose Talk to a human again. 
3. Proceed with I still need a human.
4. Click the Contact us link.
5. Select either Start messaging or Get a call.

If you have additional questions, just reply below. Have a good one and stay safe!