Getting gross profit without a purchase order/purchase receipt

Hi,
ERPNext 10.1.75 self hosted

We have several items we sell that are not stockable items but do have a cost with them, these cost are part of some OPEX cost you could say, but we want to know the GP on these invoices. I have set the sell price and buy price but the Gross Profit report shows 100%.

Is there no way to get that report to show right unless I issues a PO?

Example:
We sell 10 items at $10 a piece, we want our “cost” to show $2.00, but we get billed yearly for a large number of these units, we just want to track the cost at $2 for tracking purposes.

From what ive read there is no way to get this report to show correct unless a PO/purchase receipt or some kind of entry is added that we pay against, which isn’t possible in this case.

I looked at a few other threads and it seems this was a potential feature request but I don’t see it anywhere, not sure if this is possible or a feature request has to be added.

Thanks