We have to make a MUSE transfer as part of this transaction, so we have to pay the MUSE transaction fee. If you try a reasonable quantity of TRADE.MUSE (e.g. 10,000 TRADE.MUSE), you will see it's nearly 1-1. We charge a fee of 0.05% + the transaction fee (we're actually undercharging for the transaction fee right now, IIRC, so please don't flood us with 5 MUSE transactions).