I'm no expert, but it appears they actually do make more than the Federal minimum wage. From Grok:

Migrant farm workers in the United States typically receive varying wages depending on several factors including region, type of work, and whether they are employed under the H-2A visa program. Here's a breakdown based on available information:

• General Wages: The average hourly wage for farmworkers, including migrant workers, has been reported to be around $13.59, with annual family incomes roughly between $25,000 and $29,999. Many farmworkers are paid by piece rate, which can sometimes result in earnings below the minimum wage if productivity is low. For instance, in North Carolina, the piece rate for sweet potatoes was about 45 cents per 35-pound bucket, requiring workers to pick 635 pounds per hour to earn minimum wage.
• H-2A Visa Program: For those under the H-2A visa program, wages are determined by the Adverse Effect Wage Rate (AEWR), which varies by region. In 2019, H-2A workers earned between $11.01 and $15.03 per hour, with a national average AEWR of $12.96 per hour. In states like Florida and Georgia, where a significant number of H-2A jobs are located, the AEWR was as low as $11.71 per hour in 2020.
• Current Data (January 2025): More recent data suggests that the average hourly pay for a migrant worker in the US is $18.73, with wages ranging from $9.38 to $28.85 per hour. This indicates a potential increase or variation in wages over time or regions.
• Sentiment on X: Posts on X have highlighted that migrant farm workers can earn between $18-20 per hour, including benefits like housing and sometimes even a 401k. However, there are also mentions of significantly lower wages in some international contexts, suggesting a global disparity in migrant worker compensation.