Whoa, that's a pretty fundamental misunderstanding. While oil supply is not infinite, it's unlikely for it to be unaffordable, because before that point, people would have implemented measures to reduce their use, lower demand, and drive down prices.
I understand that your/the author's point is more subtle than "oil is infinite", but the end result is much the same (e.g. opposing energy taxes.)
You may be right: e.g. abundant nuclear power and advances in chemical engineering may render oil unnecessary before it runs out. But suppose that we really will need to continue using oil for, say, the next ten generations (e.g. for fertilizer). Do you really believe that "the market", including American politics, Saudis and several bigcos, will ensure that there will be sufficient oil for the tenth generation?
Anyway you can't just look at the supply side and oil in isolation. It doesn't matter what you're talking about, plastics nor energy, there are alternatives to oil. Oil can increase in price until it reaches the price of the cheapest alternative, and that's a hard ceiling. And since the price of alternatives are falling all the time, I think we'll be in good shape by the 10th gen.
It is literally impossible for a bigco or the saudis to overcharge for a commodity,
Oil is worth thinking about in terms of short term economic wellfare, but I am confident that there will never be a Malthusian oil crisis.
That said, I'm not entirely convinced that pretending that the oil supply is infinite is wise.