Well, economic predictions that rely on aggregate behavior of the mythical “average man” are subject to cultural influences, and differing uses of fuel do not have identical carbon outputs. And oil producers always restrict supplies artificially when prices are low (and if they get low enough, deep-sea drilling becomes unprofitable).
So I say Jevon’s only mostly right, at least right now, and acting individually is the way to make change in aggregate.
If you buy a Prius, you reduce pollution at the tailpipe by 90%. The cost of fuel goes down because of the reduced amount of fuel you now use, but if everyone’s buying Priapi (my official 
plural of Prius) for cultural reasons, the fuel is also being burned cleaner. Or if you buy a 98% efficient home heater. It burns cleaner, not just less. My spouse has a Nissan Leaf - the power plant burns fuel more efficiently and cleanly than a car can, so the electricity her car uses is cleaner. And so forth and so on.
I’ve reduced my use of fuels dramatically, but I have also decreased the pollution my remaining uses of fuel create. If we all do that, only the oil barons really suffer, and their response will be to shut down the more costly forms of oil production, which are the most harmful anyway.
