We are contemplating compulsory service by all Americans. “Free Market” is not a factor here. Against that alternative, we can consider a wide variety of non-free options for influencing market behavior.
You describe workers exploiting themselves: being willing to “do it for less” than a living wage. Correcting minimum wage to be a living wage keeps their slave-like desperation from influencing the labor market.
Beyond that, directly subsidizing American ag laborers corrects the follow-on market effects of anti-famine subsidies on agriculture. Ag subsidies depress food prices and tank farm revenue, forcing farmers to exploit workers. Ag subsidies directly to ag laborers corrects that undue influence on the labor market.
Sounds like they didn’t raise wages enough to fairly compensate workers for tolerating that instability.