Quite simply, the energy and capital costs of growing bushel of wheat are more than the bushel price of wheat. This difference isn’t just a little, but a lot. If I’m reading the table right in page 19 of the appendix linked, it’s as bad as 37x in 2019, and only projected to fall to 4.6x by 2050.

Paper https://www.pnas.org/content/117/32/19131

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