Some 10 million migrant workers cross national borders each year and, if they pay an average $1,000 to recruiters, moving workers over borders is a $10 billion a year business. Merchants of Labor examines the businesses that move low-skilled workers over national borders, asking how much they collect from migrant workers and what can be done to reduce worker-paid migration costs. For-profit recruiters are likely to be an enduring feature of international labor migration, which makes developing tools to improve the management of their activities ever more crucial. The UN recognized in the Sustainable Development Goals for 2030 the need to measure what workers pay to get jobs in other countries with the goal of reducing worker-paid costs so that workers and their families can benefit more from international labor migration. Using cost data from over 3,000 workers, Merchants of Labor examines the often murky world of labor brokers, travel agents, and others who move low-skilled workers from one country to another in order to explore lower worker-paid migration costs. It explains the three core functions of labor markets-- recruitment, remuneration, and retention-- and shows how national borders increase recruitment costs. New data on what workers pay to get jobs in other countries are presented, and incentives to complement enforcement are explored as a way to induce recruiters to protect migrant workers.