LD1 I understand the point you are making. The fallacy in the argument is the assumption that I would still cut and split 5-7 cords of wood a year regardless of whether I sell it or use it. I would not cut wood for any reason other than to burn it and neither would most others I would guess. So I have two options that I am willing to do.
Option #1. Forgo the wood heat and run my geo system 100% of the time and also not split wood. Result is X amount of $ per day in heat for our home.
Option #2. Cut and split wood and supplement my heat with our wood burning insert. Result is X amount of $ per day minus Y the amount of heat from our wood insert. X-Y=total savings by burning wood (regardless of how cheap or efficient my geo system is). And yes I understand there are some expenses such as chains, fuel, etc.
There is no Option #3 for me that involves selling wood.