There used to be a URL with the pricing on it with groceries from the resort sundry stores... I can't find it right now though...
What I would recommend is that if you are going to be at the resort for a long period of time that you use one of the non Disney services. Prices and selection at the Disney Sundry stores can be a tad on the expensive side, and really only works if you are buying a little here and a little there...
For the big purchases, try wegoshop.com or gardengrocier.com . We have used wegoshop.com without any issues and plan to do it again...