I'm confused about refillable mugs at YC. I was under the impression that guests could purchase a mug for about $10. However, on another board I saw a post that said four mugs (each in different colors) were in their YC concierge room at check-in. What's the deal? Do they only charge you if you actually use the mugs (sort of like the mini-bar)?? Or, are they free for concierge guests?