I think they would charge to make sure they get paid. If they rap on your beat and aren't insterested in putting the song on their own CD then how are they gonna get money selling it?
you can pay 'em and put it on your own CD and sell it yourself or get a diff. artist.
I'd think of it like an advancement. a performing artist can get an advancement on royalties for a song when its all through the label... but what if its an indy person like us? then they are gonna ask for some $$. I see it as the same thing.
you'd both still technically have to split the songwriter royalties though. so if you sell a bunch of copies you'd prob. have to break 'em off.
thats how I see it anyway. they have a name, a brand if you will. You can mess w/ Versaci or Foe-saci. they look the same, but some people pay for a name.
all that bein said, there are a few artists I'd pay to get on a track if I could sell it on my own CD which is what they probably were thinking you were doing if they were gonna charge you $$ to get on it.
I think some people are thinking "I have to pay them to feature me on their song" their standpoint is.. "you are paying them to be featured on YOUR song"
in other words, instead of using their publisher and you getting paid.. they are asking for money and wanting YOUR publisher to handle the distribution / selling of the track. Do all artists get on mixtapes for free? I doubt it. they get paid.