> If the subway costs $1 and 50% of the jump the turn-style 50% of the time the cost to ride the subway in aggregate is $0.75
No, you have jumpers whose aggregate cost is $0.50 and non-jumpers whose aggregate cost is $1.00. The revenues realized are $0.75 a ride, but the costs aren't distributed evenly. If the jumpers were caught, then the cost could decline to $0.75, the nonjumpers would pay less and the jumpers would pay more. That world is better for the half of the population that doesn't jump.
No, you have jumpers whose aggregate cost is $0.50 and non-jumpers whose aggregate cost is $1.00. The revenues realized are $0.75 a ride, but the costs aren't distributed evenly. If the jumpers were caught, then the cost could decline to $0.75, the nonjumpers would pay less and the jumpers would pay more. That world is better for the half of the population that doesn't jump.