The network storage price will find itself. The network is essentially bulk ordering storage from farmers at regular intervals.
If the price is too low, there will be insufficient supply of storage, so there is a floor under the pricing. However, costs will always be driven down to the lowest that minimum number of farmers will accept, as the network only needs sufficient storage to serve to users.
We don’t want more storage than we need at any cost; we need the lowest cost for sufficient storage. The spot price (and therefore the rate of deflation) would find itself at this threshold through market forces.