James McMurray said:Your numbers are (as so many others tend to do) ignoring that it turns your hands into d8 weapons and gives +1 stunning fist per day. Not very useful for a sorceror, but you can't ignore them when pricing the item.
But since you do not get the improved unarmed strike feat you still provoke an attack of opportunity and do not threaten the area around you with it plus you only get the extra stunning attack if you have the feat which a character with poor base attack bonus does not qualify for until at least level 16.
So, it is very not useful in general but there could be times when it comes in handy. But those times seem so remote that the extra would not change the price much.