The final price is the price that you will fill on your products inside Octo XB. It's composed of four values: Your cost of product (USD), your shipping cost (USD), OctoXB fee (15%), your profit under the product.
Let's check this infographic:
To help you, we created this spreadsheet, where you can check your final price. You can download xlsx here. This price calculator is also available on import products spreadsheet.