Suppose learning musical instruments is fun and children can have loads of benefits including to stimulate the right brain development and to make them to have better concentration. The ultimate goal is to let children to appreciate music instead of passing examinations and making $ in the future.
It is your choice to stop your kid from learning, however, please dont use the word "CHEAT", it's very impolite.
I wanted to learn piano when I was young but parent did not have $$ to support me. Now my daughter want to learn piano and I learn together with her. We learnt by ourselves and it will not cost anything but it really improve the our relationship.
Whether learning piano is expensive or not depends on 'how' you learn it? If your son is interested in it and you are affordable to pay, why don't you give him a chance? $$ is not everything...sometimes passion is more important and your son will not regret or blame you in the future. Think twice!