Disney itself does not sell a 3 day Park Hopper pass to the general public. However, some of the legitimate/authorized ticket brokers do sell such a pass. For example, at one time, Alamo (car rental agency) was offering those 3 day PHP passes - don't know if that promotion is still available. Post this question on the Budget Board and you will get other examples.
DVC does not offer a discount on PH or PHP passes. It does offer a 10% discount off gate price for UPH (formerly known as Length of Stay) passes. DVC also offers "dollar off" discounts on admission to the water parks, DQ and PI.
Best wishes -