This problem is what a point of sale software is for!
It is all too easy to take a product for whatever reason and market it, then keep handling it. The price, discounts and costs overtime go up and down and soon your shop is handling an item that has a very marginal margin and you do not know it as its hiding in thousands of products.
The other problem is that items with low-margins are almost always a waste of time and space, yet I have seen staff keep pushing these low-margin items.
Finding these items
This is a report that I suggest you run "Quantity On Hand and Price Check".
It will show you your margins and the quantities on hand so you can instantly start to plan. So it is a great place to start.
So here it is:
I suggest running this report regularly, as stock management requires continuous monitoring and management control.