Buying Mesos

Well since it's a 3rd party transcation it's wrong in the sence that Nexon said they can ban you for it and they don't want you doing it. So if they catch you then you risk your account. Obviously if it's a friend there are ways to ensure you don't get caught by Nexon, but if you mean it's wrong as it ethicly wrong to violate rules that Nexon came up with then that's a different question completely (but I don't think you mean that).