Good day, @sychan,
Joining the thread to share some more information on how inventory works in QuickBooks Online.
The cost you assign to vendor transactions will not update the cost under Products and Services instantly. The only time your item costs are updated is through editing them manually like what JasroV cited in his answer.
This is because QuickBooks Online uses the Sources and Targets concept. For example, when you create an expense for an inventory, the source of the information is the Products and Service page where you initially set up its costing.
Since the entry will use the data from its source, the process can't be any other way around. That's the reason why anything you manually entered on the transaction, regardless if its the price or cost, will not make any changes to its source.
The process you're doing with inventory receiving is fine. The only thing you need to do if there are changes to the costing, is to do it manually. This is to ensure proper reporting for your financial statements and books.
Learn more about inventory tracking using the links below:
Let me know if you have other questions about this. I'll be right here if you need anything else. Have a good one!
