Here "cost" is a euphemism for stupendous amounts of energy. Producing it would take up a lot of land in PV panels. That'll only give you a little extra forest and entire agricultural states covered in PV and vertical farming towers instead. I could imagine some rich, arid countries trying this but not ones with fertile soil and rain. It's hard to compete with the free fusion reactor floating up there.

From the appendix¹ (assuming I am reading this right):

   Value of production      405,329$/year
   Cost of energy        15,987,286$/year

   Area of field for equivalent yield   6,333,272m²
   Land Area Required for PV Array      4,157,293m²

¹ https://www.pnas.org/content/pnas/suppl/2020/07/22/200265511...

In addition, it is more dependant on modern supply chains. Modern farms are already pretty dependant to get their yields. We should think long and hard if we want a long term power outage to cause food shortages.