Famine likely caused as an aftermath of war and collapsed economic/trade systems.
Matt 24:7 For nation shall rise against nation, and kingdom against kingdom: and there shall be famines, and pestilences, and earthquakes, in divers places.
Unfortunately this is just the beginning of trouble.
The above verses seem to say the belief in Christ will be born in Israel during these times of trouble.
A measure of wheat for a penny, and three measures of barley for a penny;
Wheat is 3x as expensive as barley. Differences in prices are an economic law of supply and demand. Barley grows much better under non ideal circumstances like drought that will occur during the time of the 2 witnesses.
Revelation 11:6 “These men have power to shut up the sky so that it will not rain during the time they are prophesying; and they have power to turn the waters into blood and to strike the earth with every kind of plague as often as they want.”