I read somewhere that Nicki was 100k.
But im sure it just depends on who you are. Because she did a song with W.Flocka and I doubt he paid her 100k since they been cool before the fame. When his mother use to manage her.
I'd say it depends. If they co-wrote it like Alicia Keys & Emeli Sandé, it may not cost a lot as it'll make an album (in some cases). If it's a single release remix, then big bucks I think.
A lot of times it doesn't count anything monetary per se. Because when you get to that level, that kind of money doesn't really matter. If anything it's more about favors. Like you do a song with me, and I'll do a song with you or get something else in return.