A dealer told me it is ginseng so I am going with his word. Besides the tissue sample says the same thing. The root's I have here look exactly like what you have on here and what I have seen on Ginseng roots off of google. I have to believe what I am hearing and I will gladly share what I get for this root.
Steel, I'm a new beginner at ginseng. These guys on this forum know what they are talking about. Been doing it most of their lives. Their grand parents taught them. People have been hunting ginseng in the Appalacians long before California had been developed. If in doubt, why didn't you have it tested for gensenosides, not tissue. Have a sample sent off for genoside levels. That will tell you everything. No guessing. At the end of the day, that's what counts. The healing properties, pure and simple.
Your plant is almost certainly Aralia. Third cousin to american ginseng. It is the only relation to ginseng that grows in California.
It does have some medicinal value, I do not know its monetary value.
I believe it is sometimes called spikenard.
If someone is offering $400 for it, You may want to take it. Be glad as well, if it were panax q.. you would be in trouble since it is illegal to harvest panax q... in Cali.
I've lived my entire life in ginseng native regions,I've not dug myself that long but I've seen seng all my life so I say if you can get $400 a pound you better do so and quickly,if you really want to find out what it is,take it to a dealer in chinatown
Well, I don't think it would be honest or even legal to sell something to someone when you have reason to believe it is in fact something else.
That plant and root is definitely not American ginseng.
If the buyer you talk to knows that you suspect it is not in fact ginseng, but he insists, and you inform him of this...then it is on him. Otherwise, I think you would be being dishonest in selling it as ginseng.
IMHO>>> i have to agree that this does not look anything like our favorite herb. If you dealer is convinced that it is, then you indeed have a dilemma.. take his $$ and run -or- not. either way you go with this, you are taking a course that will be inheritly unsatisifing, as you don't know the true nature of this herb.
I say dilemma, as when i look this up as aralia, I see that there are seven  types and at least 5 of them are poisonous. Since you harvested this, perhaps you can remember what the top growth looked like. I have provided you a link below to looks at the different Aralia plants.