Dallas here from the Shopify team.
I completely understand you wanting to not show the price difference to your customers. In that case, you would need to write to the supplier and ask them not to include any papers and documents in the shipment.
When you order the product in Oberlo there will be a section where you can add order notes. You can write in there that you don't want anything but the product shipped.
That should solve the problem, but if you have any more questions please let me know!