Each Openprovider membership plan includes a number of cost-price Spam Experts filters. Each filter is renewed on a monthly basis. Suppose you have 50 domains, with incoming and outgoing filters on each one. 100 filters renewed monthly means 1200 SpamExperts operations will be billed each year. If you start the year with 250 cost-price SpamExperts operations, this means that 250 of those operations will be billed at cost-price, and the remaining 950 will be billed at the regular membership price.