Revenue is the specific amount of money that a company receives during a set period of time. If the cards are selling for $3 each, then the income generated from the sales of the cards can be calculated by $3 x 20,000. This results in $60,000. Then, you can subtract the income generated from the cards from the cost of the cards to produce the actual revenue. $200,000 - $60,000 = $140,000. There is no revenue yet this month, because they have not sold enough cards.
