Additional threads can be purchased from user panel if you have CapMonster Pro. Threads are sold by portions with the quantity of 30, the price is equal to the price of CapMonster Pro version. The costs is calculated taking into account number of months remained till the end of current subscription period. For example, you have been using the program during 7 months and 10 days, and would like to buy 60 additional threads. There are 5 months remained till the end of your subscription, and additional threads will cost for you ($97 * 2 portions) * (5 / 12 months) =~ $81.
*If there are less than 2 months left till the end of subscriptioin period, the costs will be calculated as for 2 months.