Hi there, andriarad. 

Thank you for your feedback and for providing some insight about updating cost or sell price on inventory items.

In QuickBooks Online, you can change the initial cost of the item by going to the Sales menu. I'll show you how:

1. Go to the Sales menu from the left panel. 

2. Choose the Product and Services option.

3. Find the item in the list that you will need to correct and choose the blue Edit button located on the right side of the screen.

4. Now on the Edit screen, scroll until you find the area containing the Starting Value hyperlink and click. 

5. Finally, here you'll see a box labeled as "Initial Cost". Enter the cost of the product here and Save and Close.

Please refer to this article to see steps on how you can manually enter your inventory products and the details associated with the items: Add inventory products in QuickBooks Online.

Also, you can find more ways of how QBDT and QBO are similar and different by looking through this link. Although they may be similar in features, the products have different layouts. If you need any further information, don't hesitate to ask.

If you have any more questions, please don't hesitate to reach back out. I'm always a comment away!