Considering that 'Bitter' is one of the four fundamental taste, along with a very common english word, and 'Bitters' being a common name for dark chocolates/bitter candy, this could fetch you mid xxx if sold correctly to the right reseller, maybe low x,xxx to a an end user (hell, speculating on end user prices is pretty absurd...an end user might pay ANYTHING)
update..
Just checked wikipedia
Bitters also seems to be some concoction of herbs/alcohol used as a digestive aid. With that in mind, I would put this as mid-high xxx