Those tariffs are also a joke in and of itself. As we can already from the oil price cap idea you can only enforce things when the world plays along, but looks increasingly like the global south is fed up by these dictates. So good luck enforcing carbon caps and tariffs when the majority of the world population doesn't play along.
You can still have them, but ultimately it's the people in western societies that will pay the price with their own pensions and social services gradually degrading.
It may be worth less, but it won't be worthless. I have a hard time seeing another fuel source for long distance aviation (although we may move to synthesized fuel in the future).
Companies will also need feedstock for plastics - that use won't be affected by carbon caps at all.