Yeah - I'm actually quite intrigued... I can't seem to come up with something you can't buy that could be a "drug of choice." I suppose it depends on how drugs are defined. I generally think that things you can't buy are like love, family, friendship, happiness, sadness, etc. - I can't see any of these being considered drugs though... hm...
You raise a good point, perhaps a bit more explanation is warranted. I have never had any interest or involvement in drugs (aside from a good Excedrin, and a 10 year infatuation with nicotine) in the traditional sense. I suppose my perspective is different on what "drug of choice" might mean. I tend to associate the phrase to anything that makes me feel happy. In simpler times, my drug of choice might have been a square of Godiva Dark Chocolate. I suppose things can never really remain that simple.
Money can't buy love, family, friendship, happiness, etc. but it can rent them. For enough money, you can make someone act like they love you for a night or buy a friend for a time, or get the things that will make you happy for now.
I suppose if you were able to accept the fact that it was all just a sham. I'm not sure that I would even want to go down that road. I guess there are some situations where it might apply (ones where you aren't really that emotionally invested). Personally, I would find it even more distressing knowing that the person I was compensating to be my "friend" were only in it for the money. Way more distressing than just not having what I wanted to begin with.