I don't recall the exact price of the toffee, but I think it's in the $12 range.
They rotate through a variety of handmade treats at the Candy Palace (e.g., Toffee, Nuttles, Peanut Brittle, etc.), so it varies from day-to-day what they have in stock. They were having some issues with the toffee (I think it might have the nuts?) a while back, but I haven't heard of any other issues with the Toffee since then. Whenever I've gone, Toffee along with Peanut Brittle were the two most common candies being sold/made at the Candy Palace. I would just ask your friends to check each day to see what is available.