Black Walnut tree value.

A co-worker and gear head friend and I went to lunch today.
He and his brother in law were cutting firewood for the garage last weekend.
They cut down a black walnut, he said they did not cut the straight piece up for firewood, because they thought it would be worth something.

He said the log is straight and about 12' in length and around 30" in diameter.

My question is how much is it worth?
He just wants to know fair market value so they do not get ripped off.

Thanks
Dried and slabbed ,it worth a bunch. Log wise it goes down dramatically. Sapwood (or heartwood), limbs scaring and any punctures also kill the pricing I just bought 3 slabs of 2"T x28"W x 120"L black walnut that I have to dry and paid 105.00 each. but they were not knot free or defect free. some of the better ones went for 150 each. I could have bought a nice straight metal free trunk 16' long 27" diameter and had it slabbed for 465.00 plus slabbing for 5.00 per cut, but I just didn't have the extra money for it at the time. (again it depends on your location too.) I'm in Florida so it's cheaper down here. Commercial cariers sell it by board feet. and it's dried straight and ready to go , so it will be prime prices .