If they cost 50 cents wholesale, then what would you charge for them in your concession stand? If you go too high, then all the White Castle fans who are used to getting bagfulls of these things for cheap may not care to partake at your theater. But, I guess it's the same as all the other concessions. Captive audience equals higher price tolerance. Just not sure if it would work with this item. It seems to me that White Castle is really aimed at budget minded people.
If you've never had one, I'd say that White Castle restaurants and burgers remind me a lot of Krystal burgers for those of you in the southeast.