Can someone show me a chart showing the issuance of Sia over time? How many exist now and how many will exist after the initial issue? And you appear to have a perpetual block reward? That is smart.
Impromptu prepared block reward and net coin supply charts here:
http://imgur.com/a/OocoUCorrect, perpetual block reward: 30,000 Siacoins after block 270,000.
Added in edit:
So a motivated miner could conceivably mine for their own permanent storage on the network at any given time?
Correct. The other way to acquire Siacoins, besides mining or buying, is to rent out storage space: you set your own price minus a 3.9% tax that goes to Siafund holders (10,000 Siafunds issued; devs/founders possess about 9,000 of those, and ~1,000 were distributed in a crowd-sale to fund initial development).