They only charge 18$ to withdraw money to an external bank, no other service fees. And what's the "Tos" mean?when we try to open an epay account, we are asked to fill in some information such as basic info,
So there is one source of income. ToS means terms of service you usually have to accept them when you create an account. Its the legal fineprint, even though some terms might be illegal depending on your juristiction. A basic profile (full name, mail, age, all correct data) might be worth a few USD, but that creatly depends on the data quality.
I think you are right, user's profile info itself is wealth.