Mug cost $18.99 + $1.24 tax each when we purchased two at BW Bakery last month. For BW, refills as Bakery, Leaping Horse Libations (pool bar), and Bellevue Room (at breakfast for both coffee and soda; don’t know about evening bar service).
I know you can refill mugs at self-serve station by Hurricane Hannah’s at YC/BC, at the BC Marketplace (now a Coke Freestyle machine at that location), and at the YC quick serve Ale & Compass Market (also Coke Freestyle machine).