Stockfish is only slightly weaker, and is open source.
What's the point of closed source chess engines when a lot of engines are already far stronger than humans? Who's going to pay the money for a closed-source chess engine? Idiots? A grandmaster may want it to study its playing "style", and chess algorithm researchers might want it to study it, and other chess engine designers might want it to reverse engineer it, but there's no practical reason for even a strong chess player to buy chess engines anymore.