I believe it was probably more like this:
Dylan: Hey man, let's do another line of that meth!
Guy with meth: I ain't giving you no more free meth. If you want more of it, you're going to have to do something for me.
Dylan: Uh... what?
Guy with meth: You gotta suck my dick.
Dylan: I thought you'd never ask! I mean... Uh, if you want your dick sucked man, you're going to have to give me TWO lines.
Yeah, I ain't sucking no dick for less than two lines.