Answer:
Historically speaking, some southern states have benefited from convicting more African Americans as they could use them as free labor. Some ways they specifically made money from this are;
After the Civil War ended and enslaved people were freed, plantations in the South needed cheap labor like they were getting from enslaved people in order to make profits and rebuild a Southern region battered by war.
They turned to the State which leased out prisoners to them. In states such as Alabama and Tennessee, the state made huge profits from leasing out prisoners who were then worked to death by their leasees. By convicting more African Americans, the states ensured they had more prisoners to lease.
When the states saw just how much these leasees were making from being able to use cheap labor, they became envious and started their own plantations. The plantations bore huge profits and made states richer. In order not to attract too much attention they convicted more African Americans so that they could use them to work in these plantations.