Answer:
The main benefit of slavery to the colonies was that the man power was completely free of cost. They did not had to invest in them. The slaves were not compensated for their labor work.
Step-by-step explanation:
The main reason why colonies were built was to take over the land and their people. White people would buy slaves for a lifetime. They would treat them brutally. They did not care about their feelings. They were owned as their personal belonging.
Free labor meant whatever the revenue was being generated by the slaves, all went to the white mans' pocket. There was no retribution.