If he offered you that much right off the top with all that work thrown in to boot, I’d hazard a guess that you could have gotten a lot more for them.
I really don’t know. But I do know they grow fast from fallen ‘fruit’. I have one at the end of the covered porch which was no thicker than three inches sixteen years ago. Now, it’s taller than the house, eigh inches thick, and a ‘climbing runway’ for old crooked-tailed cat to come to the dormer windows over the porch. Another one started from a fallen nut at the front of the porch just eight years ago and is already taller than the house. Two on the other side of the driveway in fron of the house are shooting up at an almost alarming rate, but they’ll shade the garage front of the house in a couple of years!