Well, if they consent, that makes it okay, right? And they're both of age, too, so what's the problem?
Here's the problem.
Sex is a great thing. One of God's greatest gifts. It allows for the creation of new life, and it probably feels great. But you see, abusing this most holy thing by masturbating and doing it to sell on the web for money is just horrible. Even if God is taken out of the equation, that still holds up. Sex is a beautiful thing, and it shouldn't be abused for the disgustance that is porn.