Classicfur,
That does seem like a small number of roots to make a pound of dry (or 3 lbs green).
Just looking at the pic they do look like some decent sized roots though.
I am sure you remember this pic from my birthday hunt last year.
That root - I found growing on a bluff - in that rocky (no doubt mineral rich) soil and I found several like that there and they all looked about the same. Big Ball Roots which all seemed to be very young (5-8 years) old and that one weighed 1.5 oz (green) and as you can see there just is not much of a root neck on it at all - fairly young root.
It would take 32 (1.5 oz roots) to weigh 48 oz or 3 lbs green.
107 roots that weighed 48 oz - that would be about 0.45 oz per root.
I would say that is definately possible in ideal growing conditions for 9 year (or possibly even younger) roots.
TNhunter