I added a PS, but these value adds stop being a farm. If you operate a cheese factory that can create a lot of value from a small area, but it generates value even if you use milk from a different farm. Operating a stall is again a way to generate revenue, but that's completely independent from actually growing food.
I think that's a universal argument for making all farms worthless, outside their subsistence value. All the produce must be sold; your argument means you can always argue that the value comes from the selling, not the farm.
I am simply making a statement that differences in quantity become differences in kind. You can separate things by revenue generation.
If you buy from 1 farmer and then sell wholesale to 1 customer your not going to make significant money. If you buy from 1 farmer and then sell at a stall to 1,000 people you can make meaningful profit.
