How can I add an extra cost to dropshipping orders without affecting customer prices?

[BRIpothecary]

Our e-com store runs a 3PL fulfillment with a mix of dropshipping. I want to be able to add an extra cost to the order for dropshipping due to our margins being drastically different from what we had in-house at the 3PL. Is there a way I can add this cost to cut into my margins only and not pass that on to the customer? They pay what the product's price is. I'm ultimately trying to solve how much margin we are losing by staying with a hybrid dropship model instead of stocking more inventory ourselves. I don't have access to the outside bookkeeping, so I'd like to be able to solve this mystery on my own. Ideas?  

[Mirdas]

hi @BRIpothecary ,

Given that you are not passing on the additional charges to the customer, how about extracting sales data by product from Shopify and then calculating the profit margin?

[BRIpothecary]

Thank you Mirdas,

That's what I started working on last night after sending out this
question. I'm thinking longer term with visibility regarding this issue and
with ease of use for my team coordinating dropships. Ideally, I'd like to
be able to add a line item that has a cost but not a retail price so it
only reflects the actual margin of the sale but doesn't affect the
product's cost so ultimately I can search all my dropship orders based on
that line item and I know my margins are "x" on average for dropships.
Annoying but vital to understand.