i always see it new for $20.. so yeah, its gotta be around 15 used. definitely worth picking up, even if the next game comes out in march. there are going to be alot of control changes in Champion, & i dont know how i feel about all of them. for one, no more going through the motions of the punches to pull uppercuts & hooks, etc. in champion you'll simply flick the stick in a direction to unleash a punch. personally i enjoyed the way it was set up in round 4..
my point being though, i think 4 will still be worth owning once you have Champion.