It's sloppy terminology. I am fairly sure that "cash crops" was intended to mean "high caloric density, mass market crops".
While millions of people do eat hydroponically grown/growable produce, they do not survive on these kinds of crops. They rely on root vegetables and cereals for that, and those are currently impossible to grow in the way described in TFA.
> "cash crops" was intended to mean "high caloric density, mass market crops".
Tobacco is a cash crop, not caloric dense. Cash crops are the profitable crop a farm might use to generate cash. Since all farms are now commercial this isn't a meaningful distinction but it was when most farms were substance.
Wheat and Corn are not traditional cash crops. They are stable cereals. Cereals will be the last crops to ever become viable in vertical farming. Which is fine, the technology can develop leveraging the high value low-calory crops.
There are different ways of talking about "cash crops". The sane metrics, IMO, take into consideration the inputs required and the toll that growing takes on the soil.
From this perspective, garlic is an extraordinarily excellent cash crop: high yields, very low inputs, extremely low impact on soil nutrients.
By contrast, potatoes can generate more income for the farmer per unit area per year (mostly because of the caloric density), but they do wear down soils way more than an allium like garlic, and if you take that into account, the long term picture is not so rosy.
I've read that if you can get the timing right, the most profitable crop to grow in the USA are the flowers used at high school and college graduations. The window is very narrow, however, and if you miss it you earn basically nothing at all.
While millions of people do eat hydroponically grown/growable produce, they do not survive on these kinds of crops. They rely on root vegetables and cereals for that, and those are currently impossible to grow in the way described in TFA.