All I know is that 3 letter/characters twitters don't go for to much. Since it's a 3 letter, he'll get more than a 3 character. I wouldn't pay over $8, that's just me though. Good luck to him.
Usually random 3 letters go for about 10$, but if you find someone who really likes it, or can use the acronym appropriately then Im sure you could get 15$ or more.