Sure, most of those plants can be cheaper to buy than grow, if you treat your garden shop clerk as a used car salesman and let him connive you into buying every

Sure, most of those plants can be cheaper to buy than grow, if you treat your garden shop clerk as a used car salesman and let him connive you into buying every unnecessary over marketed garden gadget in the shop. But really, most plants will just require a shovel, trowel, cheap fertilizer, and a bit of time. Wheat and others are obvious exceptions, because their actual value is so low it's easy for any expense to exceed the benefit. Wheat also benefits hugely from mechanization, but the initial costs are high. It's basically an oddball. Potatoes don't fit that pattern, just buy seed potatoes once, then let a few grow "eyes", cut them off, throw them in the ground and weed them a bit. Done.