I have some experience in this area, having to (among some others here) overcome an addiction of my own, and having been close to several people who have had to struggle with drug, pornography (or other forms of sex), gambling, drinking, and other forms of addictions.
As has been stated already, overcoming an addiciton is fiercely difficult, even ignoring the "physical" aspect of certain kinds of addictions. There is a very strong psychological pull. However, there is one form of treatment that is generally available for next to nothing - AA, NA, and similar sorts of support groups. Certainly, this isn't exactly Rehab, but I've heard that if someone is dedicated to overcoming, and is willing to attend 2-3 meetings a day, the success rate rockets.
One thing I want to challenge, however, is the idea that addictions can never be "cured". I would assert (from personal experience) that they can be cured (from within). This is anything but easy, and sometimes takes years, even after "overcoming", but it can be done through some emotional rewiring - usually the addiction is fueled by some sort of emotional deficiency (at least the sexual variety certainly are, and I would be surprised if the others weren't similar), or "love disorder". Through obtaining a greater understanding (and love!) for oneself, this deficiency can be cured, and the desire for the addictive thing largely eliminated. True, there will be residual wounds that will always remain, and if one were to emotionally revert, the addiction would like resurface, but if one can develop and sustain a healthy emotional outlook, it is my opinion (and experience) that addiction can be "cured".
However, my heart goes out to everyone who is struggling with addiction of any sort. I know how frustrating and challenging it can be to deal with that sort of thing.
