Consider the term cash crop.
Cash crops are agricultural crops that are planted for the purpose of selling on the market or for export to make profit, as distinguished from subsistence crops planted for the purpose of self-supply of the farmer (like livestock feeding or food for the family).
— Eurostat
In common usage, though, it would be unusual to call this an indirect product.
Consider a farmer who plants corn.
It might be clinically correct to say that the thing raised is the whole plant, including the stem, roots, flowers, fruit, etc. You also can't be faulted for saying that the farmer isn't selling farming services, where he'd be paid for tilling, watering, harvesting and so on.
However, in common usage, the thing that the farmer is said to 'plant' is the corn. The tilling and watering etc are just part of the cost of doing business, so to speak. By the same token, the roots, stem and so on are the by-product, not the main focus of the planting. The whole farming enterprise has (in this case) the corn as its main focus.
So if you referred to the corn as the "indirect value" of their efforts, or the 'by-product' of what they grew, they'd probably tell you that the corn was instead the centerpiece, the whole point of their endeavour. Take away the corn, and there'd be no point doing any of the farming work.