Adding inventory - same product, different cost

"Currently have inventory loaded of medical wristbands eg: 10 bands @ R50 ea"

You should not enter the qty and cost in the new P/S item set-up screen, unless you are starting a new set of books for an existing co.  The offset goes to Opening Balance Equity, which should have a zero balance, when you are done entering all the balances from the opening Balance Sheet (if you are starting a new set of books for an existing co.), and should never be used again.

Once the books are set up, use an Expense or Check (if you paid from a bank account) or Bill (if you will pay later - offset goes to Accounts Payable) when you purchase stock. If it's a new P/S item, you can create the P/S item on-the-fly, from within the purchase screen, But enter 0 as the starting qty in the P/S item set-up screen. You can enter a cost here (optional) but it is just for populating future purchases. It does not ever change

There is no New Product involved here. It is the same product; each purchase is where you list what you got. The Point of having a system managing FIFO means it tracks each time you replace stock, for that Same item, at varying cost. All you need to do is keep entering that you Bought more of that same product, if it was that same product that already exists.

So do you do consulting work to help someone set up their manufacturing company? 

@joannamidolo 

There is no specific feature in QBO for a manufacturing company (e.g Assembly). You need having a 3rd party app to integrate with your QBO.

This wasn’t a how to in quickbooks.  I have desktop enterprise. This was more of a concept question.

If you are not using QB Desktop (outdated) South Africa version, you should post your question with a new subject in other community (e.g Canada, US).