Ok, this is'nt really a scamm, but you're "Tricking" the seller to send you money and the item you we're supposed to "buy", all you have to do is to be with the Trade Channel, and look for somebody to say "WTS (item here), make an offer, no bullshit" or something, where you have to make an offer, (works if they set a price, but easyer if you make an offer) lets say someone is selling Nightblade, for an unknown price that you'll have to set, (Lets say its for about 100g on you'r server) then tell him you offer 300g, and send it fast to you'r main character "You'r main character's name" and plz hurry because you want it fast, now, if they believe you will buy it for 300g, that ofc you wont, they wil hurry to a mailbox, put you're name in, insert the item, set 300g, and then press send, and then (if you're lucky) they forgot to check "C.O.D" and they will send you Nightblade and 300g, but if he rememberd to check "C.O.D" you will get the mail, then just ignore it and he wont get it back in some time AND he will have to pay 30c so you "Scammed" him for 30c ^^ (i think you'll have to pay 30c for C.O.D mail)
(But make sure the victim have 300g and 30c or selse it will come up you cant afford that or something, then they check it, and send it)
Worked for me some times (not for lvl 70 epix)