Nevermind, found the info on a handy site someone here has..
Refillable Mugs
For those people who drink coffee like I do, one of the best deals in the campground is the refillable mugs. Buy a mug at Trails End for about $11.50 and fill it up anytime you want for your entire visit. At Trails End you can select coffee, hot chocolate or fountain cold drinks. At the Meadows Trading Post coffee and hot chocolate are the choices. By the end of my last 5 day visit, my cost for a cup of coffee was down to about a quarter