The commission depends on the currency used and it's trading volume. A trader who places an order pays 0.1% of the transaction amount. Anyone who closes a deal pays a commission, depending on the currency's trading volume for the last month.
When operating with US dollars, the commission is calculated as follows:
Up to 50 BTC — 0,2%.
From 50 BTC to 0.18%.
From 200 BTC to 0.16%.
From 600 BTC to 0.14%.
From 1500 BTC to 0.12%.
From 5000 BTC — 0,1%.
From 10,000 BTC to 0.08%.