The percent commission changes based on the price of the sale. Higher priced items are charged a lower percent. So, as the exchange rate changes, the bitcoin price of items not pegged to bitcoin changes, and so therefore the commission on them changes. It's inescapable unless we created a different commission schedule for every currency. Instead we just use one and base it on bitcoins. This is correct. Also, if you want to make sure you always get the same dollar value expected for your orders, use pre-commission pricing, escrow hedging, and peg to the US dollar.