The support team answered you exactly as it actually is: When we receive a user's payment, we first pay the payment gateway a processing fee, the sales fee is calculated after the payment of the gateway fee. Different gateways may have different fees, so your payout per sale may also vary slightly. We cooperate with various payment gateways to ensure a constant and uninterrupted acceptance of payments.
Maybe we're not specific enough. Let's say a subscription costs $100, and your share is 50%.
The user's payment is processed at the payment gateway of MP's billing partner, first we pay the payment gateway commission, the commission can reach up to 50%. Let’s say the commission is 30%, therefore from 100 dollars the MP will receive 70 dollars, respectively, the partner will receive 50% of 70 dollars, that is, 35 dollars. You received from the sale of 90 days on FB 20.98: 18.88 and 2.1 on the insurance balance. Therefore, we received 41.96 (20.98*2) from the payment gateway. Is that clear now? The problem is that you would earn ridiculously little even if you received 110% of the user's payment amount.
You have few files and these files are interesting for users. Most of your traffic is from India, but our prices are too high for this market. You need to publish content that is popular among Europeans and Americans. More than a year ago, I already answered you in private messages to your complaint about low sales. But I see that you ignored my advice. I'm afraid I can't help you.