The ability of the PUT cost in Safecoin to adjust to demand will depend on the network’s sensitivity to fluctuations in the level of free space available.
If demand for resources drops, free space available increases, and the network can adjust cost per PUT in terms of Safecoin accordingly, and well before farmers have time to increase capacity on the network.
My hope is that the network will be able to detect a drop in the level of data being put onto the network vs new space being made available, and will be able to use that information to adjust the price of PUTs in Safecoin on the fly to avoid the scenario you mention.
It would be very worrying if the network were so insensitive to changes in demand that a spike in the price of Safecoin affects the cost of putting data on the network to any significant degree over any significant time frame.
It would be a significant failure if the network encouraged farmers to contribute more resources in the absence of any increase in demand.
If the network cannot sense a drop in demand, a price swing wither way in Safecoin could seriously damage the network and reduce its usefulness, sending confusing price signals to participants & moving away from a balance of resources. A low degree of stability in the USD price of putting data onto the network would also hinder adoption significantly.
But, I don’t think it needs to be like that, especially when there’s not even test Safecoin yet. When it comes to implementation, I’m sure the devs will consider ways of making the Safe network’s internal market highly functional and responsive, even if it requires new ways of achieving that.