Demonstrate what happens when a steel ball is allowed to roll down the ramp into the others. It stops and one at the other end takes off. Because energy is nearly conserved, this one rolls up to just about the release height of the other ball.
Do it again and the second ball shoots off the end of the ramp. Why? Well, you’ve exchanged a normal sphere with a magnetic one. It takes energy to pull the magnetic sphere away from any of the others. Hence when separated at the top of the ramp, it has both gravitational and magnetic potential energy. This energy is converted to kinetic energy of the one at the other end. As it rolls up the ramp, kinetic energy is only converted to gravitational potential energy. There is plenty of kinetic energy left.