Honestly it depends on who wants to buy it,but there is not alot of difference as far as dealers, but people who use it personaly if you know someone like that will for sure give you a better price for a single old root.
That's one big n chunky root, can ya weigh it and count the neck scares? It would be nice to know the age and weight!It looks like it is around twenty or so years old but the necks not in focus for a accurate count.Fits with your grampa's plantings eh?
From the picture,selling it dry may be an advantage.It appears to have nematode damage,that is the small balls on the fine roots. You should dry it and remove all evidence of the infection and put it in with your normal sang for the best price.
That is how they try and count it bowhog,but after knowing where plants are and watching them grow,I can tell you that the old timers where not wrong when they said that seng does not come up every year ( wild seng ) I have learned 1st hand that this is true.It is for certian thou that for every scare there is 1 years growth but how many years in that time did one not come up,thats what makes it very hard to judge the age of wild seng especialy roots like this one.