The Ultimate Park Hopper is offered only to WDW resort guests. I cannot be pre-purchased at the
Disney Store.
Guests reserving rooms through CRO or WDTC can pre-purchase the UPH at a lower price, and have the purchase of the passes linked to their resort ressie.
However, because of the unique nature of the
DVC program, DVC members CANNOT pre-purchase the UPH. They are still eligible to purchase the UPH at check-in, but must then pay the resort price (as listed by tigger2005).
That said, DVC members DO get a 10% discount on the UPH. Technically the discount should not be available to those renting points, but the resort CMs do little to investigate further. As long as you are staying on points, they will typically allow the discount.
Thus, if you wanted a 6-day UPH, the total price would be $301.93 ($335.48 less 10%).
When purchasing the UPH at check-in, CMs will usually let you "drop" either the arrival day OR departure day from the UPH. Other than that, it's designed to be a Length of Stay pass. If you have a reservation for 8 nights, you need to purchase the UPH for 8 nights (or 7 if you drop one day).