You can change items prices by importing products into QuickBooks Online (QBO), user35184.

Let's export items from your account beforehand, so you have a copy of it. 

1. From the Gear icon, choose Products and Services.
2. Select the Filter icon, choose Inventory from the Type drop-down arrow, and choose Apply.
3. Click on the Export icon.

Then, update the price for each item and save the file to your computer. Once done, you can now import the data.

1. Click on the Gear icon and select Import Data.
2. Select Products and Services.
3. On the Import products and services page, select Browse.
4. Choose the file and click on Open.
5. Select Next and map your fields to QuickBooks fields.
6. Click on Next and ensure to check the Overwrite all values for each product or service that you import with the identical name. (This can’t be undone.) box.
7. Select Import.

You can learn more through this link on how to import your products and services from Excel to QBO.

In case you want to merge duplicate items or remove unused ones, refer to this article: Remove or merge a product or service.

Keep us posted if you need anything else. We're here to help.