On the one hand, it is good to know that in case you have stuff that does need to be refrigerated -- medicines, baby bottles, a stash of Red Bull -- there's an option to keep it all cool that doesn't involve repeated trips to the ice machine. On the other hand, it is $35. But, that does beat the penalty fee of $50 so there's that.
And, for what it's worth, the minibars at MGM Grand are pretty well-stocked. Aside from the usual accoutrements -- Coke, water, juice, Budweiser -- they also sell gourmet items like white-chocolate covered raisins ($15), coconut water and Hylunia skin products. But, just remember, if you even slightly move one of these items, you will be charged. So make sure that high-end therapeutic bath soak is worth it.