I agree, the $50 price tag is a bit nuts but it isn't out on its own. Using the Six Flags pricing that was mentioned earlier in the thread, I thought their $40 mug was insane so I bought multiple all day mugs for $15 each (free refills on day of purchase). Then would buy a $6 dollar wrist band for all day refills on subsequent visits. They got $51 out of me by the end of the season on that drink cup. Should have just sprung for the $40 mug up front.
When I visit SDC, I'll bring my old n trusty mugs while they're still honoring those printed refill prices since those include specialty drink pricing. I'm not sure if the $50 mug includes the delicious frozen lemonade refills.