I am surprised by your knowledge about Korea fut & Opt market. Now the premium of call 85 (ATM) is 3.30 and has been traded 45,243 contracts by now. - we still have 2hrs 50 min more before mkt close. With this, let's calculate the commission. When you buy one contract of this option, the formular is following; 3.30*100,000won*0.5%=1,650won($1.32) 100,000won is multiplier and 0.5% is commission rate. The commission rate is negotiable. The more you trade, the cheaper commission rate is. If you have any question, post it.