As to this specific case, I finally spoke with an actual human who acknowledged the problem--the PSN Store was slow to update and falsely listed the game as in the IGC when it had already expired--and granted a refund to my credit card. At least that is what he said would happen; I've yet to see this, so the possibility of a chargeback still looms.
More generally, I find your mindset confusing and troubling; what you're expressing is the kind of might-makes-right thinking that values power and size over reason and justice. Why should Sony have a privileged position in this transaction? I chose to exchange an agreed upon amount of money for an advertised service (advertised, to clarify once more, at the actual point of sale). Why does Sony get a free pass for not upholding their end of the bargain, while I'm on the hook for the money I gave them?
Commerce is built upon the idea that all parties are honest and aware of the terms of their trade. To return to an earlier example, let's say you bought a dozen eggs at the store, but when you got home you discovered there were only eleven eggs in the carton. When you returned to the store to ask for either the missing egg or a refund, you were informed that the store posted on its blog that all egg cartons marked "12 eggs" in their store actually only contained eleven eggs, and you were a fool to think you would receive twelve eggs. Is this fair? I would like you to actually answer this question.
You say that I've made a tactical error in saying I will never again buy from the PSN store, and I agree. You warn that if I cancel payment I will lose my PSN membership, meaning I will not be able to buy anything else on the PSN Store ever again. I have stated that I never want to buy anything from the PSN store ever again. I hope you see that we have made the same mistake.
Finally, my interactions with you on this board (I know you're not a Sony employee, but you act under their imprimatur), coupled with my awful first experience with customer support, have succeeded in making me cancel my PS4 preorder. I guess I should have threatened this sooner, strategically, but I saw no need to do so in such a cut-and-dry case. Another of my mistakes, I suppose.
I'm pleased to report that Sony fixed this problem to my complete satisfaction. It didn't take much to placate me, just an acknowledgement that they were in the wrong and a minor amount of PSN dollars. Now I can continue to purchase things from Sony, they can continue taking my money, and we can all be happy.