if they guy buying it said hey think you can get that for me, im willing to pay this much.... and the guy selling said hey see if you can find someone to buy this for me...then theres no reason the middle man shouldnt make a quick 10 or 20 bucks for his time. not 50 thats a lil much.

now if the guy selling and the guy buying do know eachother and make contact but your buddy is trying to stay in the middle thats wrong.

i could see pocketing some if they are both using you to facilitate the sale, but if your just putting them in touch with eachother then no thats wrong.