It's completely applicable if the returns the bank can make are less than the operational costs associated with storing your money. The offered interest rate is

It's completely applicable if the returns the bank can make are less than the operational costs associated with storing your money. The offered interest rate is going to be some function of the bank's operational cost subtracted from the bank's investment return. When interest rates set by fiscal policy are so low that the bank can't make enough through investing deposits to offset the operational costs, negative interest rates must occur.