I don't think there's a return on investment formula for fantasy baseball, I think it's just a general term used for whether a player exceeded his draft spot (value) or not.
I haven't found much on this but it seems interesting, I have seen a magazine with the current auction values and the values of last year (with a guy that was bought for like $30 and missed the year, his value was -$30 obviously). But what if a guy was bought for $40 and he ended up at $42... how do they calculate that?
I'd like to see how the formula works. Like if Trout's average value is say $60... what stats does he need to achieve just this value? his projected stats? Are all the players current values based on their current projected stats? Does it work with how they are ranked at the end of the season... so if Kemp finishes #1 overall, his value is $60 (and if he was drafted at $40, he players +$20).
Also, the main point for bringing this up - I'd like to see last year numbers and next year when it comes... how many guys really perform over $30? what percentage of pitchers in the $10-15 range exceed their value, stuff like that.