Since i sell Yahoo Answers Level2 and level3 accounts so i might be able to give you a little rough sketch on that If they are standing at level5 or 6 or higher they certainly worth $30+ and if it has top contributor tag it would make it much more valueable.
But the Question really is i mean Level3,Level4,level5..... Level8 they all do the same function (Posting Clickable) Links so shall one invest and risk all that for a higher level or shall they buy multiple Level2 accounts so that can multiply their chances from preventing suspension and posting Clickable links.