The ideas are powerful, but the garden is not a useful way to think about food markets. Pollan does not acknowledge how much his garden construct is historically specific. Early crop-growing, circa 5000 B.C. or even 1700 A.D., was no fun. The labor was backbreaking, and whether it rained, or when the frost came, was often a matter of life or death. And proper gardens—as a source of pleasure rather than survival—became widespread only with the appearance of capitalist wealth and leisure time, both results of man's dominion over nature. The English gardening tradition blossomed in the 18th century, along with consumer society and a nascent Industrial Revolution.
In other words, the garden ideal is possible in some spheres only because it is rejected in so many others. It is the cultures of the scientists and engineers that have allowed gardens—and also a regular food supply—to flourish in the modern world.
So, let us not judge food markets by whichever costs we observe on a fact-finding trip. Society uses markets, prices, and formal accounting precisely because a narrative is as likely to mislead us about social costs as not. Markets may require tinkering, but to make that judgment, let us put down that hoe and pick up a price-theory textbook.