Complex sentence: Several sports leagues have implemented salary caps, using it to keep overall costs down, and also to maintain a competitive balance by restricting richer clubs from entrenching dominance by signing many more top players than their rivals.
Split into simpler sentences: Several sports leagues have implemented salary caps, both as a method of keeping overall costs down, and to ensure parity between teams. The cap is used to maintain a competitive balance between the teams by restricting richer clubs from entrenching dominance by signing many more top players than their rivals.