Economists often use models where firms are assumed to maximize profits. Non-economists sometimes criticize these models, arguing that their assumptions about human nature are too simple. This debate over the behavior of humans won’t be resolved anytime soon.

Meanwhile, there is increasing evidence that fungi entrepreneurs respond rationally to incentives:

A study just published in Current Biology by Toby Kiers of the Free University of Amsterdam suggests that, like cunning merchants who know how to make a profit, fungi exploit resource scarcity by marking up their prices. They demand more nutrients from plants in return for their valuable mineral commodities. . . .

As [Toby Kiers] monitored the collection and trading of the phosphates from fungi to carrots she found that the fungi enthusiastically transported them across the hyphal network from areas of abundance to zones of scarcity.

Moreover, though she was unable to measure directly what price the carrots paid for their phosphates, she managed to do so indirectly. She found that hyphae growing in resource-poor patches put on more weight per unit of phosphate transferred to nearby roots than did those in patches of abundance. This, she argues, makes it clear that fungi in zones of scarcity are marking up the price of their products.

One argument in favor of the profit maximization model is that the forces of competition will gradually weed out human firms that do not behave in such a way as to maximize profits.  Presumably, over the past 200 million years the forces of natural selection have gradually eliminated non-profit maximizing fungi from the gene pool.