Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
it depends on who you're trading it in with? check their website.
 
I am with AT&T, and they gave me $200 for my iPhone 4 when I traded it in for my iPhone 5, I found they gave the best trade in values, outside of selling on ebay.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.