“You have to rob Paul to pay Peter, there is no other way. Murder in it’s simplest form, but what happens when all the money is gone?”
http://en.wiktionary.org/wiki/rob_Peter_to_pay_Paul
“Well, money becomes a matter of faith. And thats what I’m here for. To make you believe.”
This is mostly rhetorical (that is, it just sounds clever without really saying much). Remember, the character is inane. If we wanted to draw meaning from it, however, he is saying that people become devoted to money as an ideal as if it were valuable in itself (when really it has no value beyond it’s ability to get us things we want or need). Furthermore, that ideal has replaced the old ideal of God, and he’s helping with the character’s conversion.
“Do you understand what we achieved here? We made the consumer into the means of production. This thing is going to sell itself!”
This is more ranting. The means of production refers to the tools and resources used to make a product. The antagonist seems to think that if you can get consumers to use themselves up to produce the product they want to buy, then it will be easy to sell. This might make sense if the product is used to treat whatever harm is done to them by producing it.
“How does it relate to losing hope?”
One thing to keep in mind is that the antagonist is insane. Being subjected to his rantings is likely to make one confused and lose hope regardless of what they actually mean. However, there is a dark cynicism to the rantings that suggest someone who has given up on higher ideals. When you lose hope, converting away from a more hopeful ideal to a cynical ideal like money will seem more sensible.
Of course, the context of the game will tell you things that internet strangers cannot. A brief bit of research suggests to me that the character is caught between various crazed idealists. Since it turns out that the god that one of these idealists wants him to believe in is evil and that the antagonist in question wants him to give that ideal up for the cynical ideal of money, it looks like the character has no good options. In other words, his situation is hopeless.
But if you’ve played the game, you might be better able to figure out exactly how all these things fit together.