I was thinking about this more, and telling him could actually be viewed as collusion by the other teams. You benefited this other owner, and you're even saying he owes you one. In a league as competitive as $3000, I might be pretty angry if I was the guy who had the number two waiver priority, and I found out you did this.
I know you didn't mean it that way, and I'm not calling you out or anything, but there is a moral argument to both sides of the coin in this one. At first I was arguing, "screw him! It's fantasy! Take his man and buy him a beer afterwards, where he can woo you with offers."
But now that I consider this as a collusion issue, I would say you shouldn't have told him. You did already, so rot in hell!!! Just kidding.
Don't sweat it. I just thought my collusion angle would be a nice thing to discuss. Anyone agree/disagree with me that this could be considered collusion?