In terms of the motivation - getting off - it's the same for Rush gobbling down the Vicodin, or whatever his particular taste was, as it is for the skanky crack whore who hits the pipe, but let's also be realistic - Rush has, fortunately for him, options that a lot of people don't. Rush gets to go the Betty Ford clinic, whereas skanky crack whores tend to kick the habit around the same time that they die in puddles of their own blood and feces.
Ehh? Wasn't Rush's motivation pain? Isn't the skanky crack motivated by excape from the responsibility for his miserable life? IMO this is a huge differance. Once hooked the motivation is once again the same, avoidance of the pain of withdrawal. But the skanky crack addict will take a larger dose to also get high.