kda is correct--25% off of Rack Rates.
However, when the discount is offered the Member is supposed to be staying in the room. You cannot book a room using the cash discount and put a different name on the reservation. And you probably will not be able to book a Studio AND a 1B for the same dates.
Rooms are only offered at the cash discount when
DVC projects that they will not be able to fill all of the units with guests booking using points. So, it can be difficult to predict when rooms will become available. Weekends are reportedly the easiest times to get due to the higher points. For weekdays, Member Services may tell you there is nothing available at one point, and two weeks later they may suddenly have an opening. If you're looking at a high-occupancy period (December, holidays, etc.) you may never get a room.
I've read reports that you can book a room at the full Rack Rate via DVC and they will automatically apply the 25% discount later if their computers suddenly decide that rooms can be released at the lower rate. Short of doing that, you may just have to call, call and call again.
Also note that when a room is booked using the cash discount, the normal DVC housekeeping schedule applies.