You can sell all your stuff, drain the merchant, then simply swith and get a new batch of goods (and money). Also it allows you to 3x re-roll items, and unlike save/reload you can even profit from buying all 4 rolls that end up being presented to you.
Also, and this is not the exploit side, it can be very annoying if you want a particular item that vendor has, talk to him/her with the wrong character and bam... the item you wanted is now gone.
the item is not gone, if you trade again with your other character those items are there for you and that's what I find disturbing - the vendor "knows" which person he trades with and has different items for each char
(you should not give him the money to buy it on spot because then you are accused of stealing!)
