Demarcation between coins and item have been removed recently, and now coin as well as item is presented in the puzzle solving rewards and the user can choose any of them, I like that.
I suggest on this page also, do give the option of coin prize and item prize, and let the user choose one of them at a time.
Often, prizes offered in this page is such item that is already in abundance with the user, like ore, water that all puzzle rewards mostly give. So waiting for 20 hours to get one Water is a disappointment. In such a case, a user might prefer to choose the cash prize.