add to commision to total price

You could have the commission in your shipping method fees. That's the simplest way to do it. Otherwise, you will have to edit the code of the cart to handle that...

If you want to display a second price, you would first have to create a custom field of the type "product" so that you can enter your price and display it on the front end. Then, you would need to modify a bit the display so that it displays before the US price. You can do that in the file show of the view product via the menu Display->Views.