The Enrollment Act allowed for two controversial practices, substitution and commutation. Essentially, it allowed wealthier men to buy their way out of having to fight.
The policy of substitutions allowed someone who had been drafted to pay another person to serve in his place.
Commutation (paying $500 to escape the draft) was created in an effort to keep substitution prices low. In addition to suppressing substitution prices, commutation was intended to raise money for the war effort.