Lyric discussion by IvyMike 

Cover art for $300 lyrics by Soul Coughing

I think the sample, "How much? She said for three hundred dollars I'll do it" is part of a joke.

The joke goes something like this: Dude's walking down the street and a hooker comes up to him, and says, "Hey big boy, I'll do anything you want." The dude thinks, and says, "For how much?" She said "For three hundred dollars". He says, "b*tch, paint my house"

I think this might be a Chris Rock joke (or even a sample, although it doesn't sound like him)