> I am not going to look for a source right now but I would venture that since the 1960's were part of the industrial era that food was even more expensive before the creation of the Haber process and gas powered farm tools.

You are correct that it used to be even higher. The US BLS estimates around 40% of DPI was spent on food at the turn of the century (1901). [1]

[1] https://www.bls.gov/opub/100-years-of-u-s-consumer-spending....