LorrinCFA

there are multiple prices that are in effect here
Current Spot price = what you see today
Current Futures price = what you see today for say a 3 month contract
Expected Futures Price = what you would expect to see for a 3 month futures contract 3 months later. (this would be  what you calculate with the risk free rate, storage etc).
If the Expected Futures price is below the Current Spot price - this means that the commodity price is in backwardation (a downward sloping curve).
when it is backwardated - and given the usual term structure of a commodity spot curve which is upward sloping - you could expect that the futures price (in the future) will converge to a higher spot price. This expectation that price in the future WILL rise - (based on expectations) makes the producer want to produce (since he knows or is convinced that the spot price will be higher).