Hi, Bryan, and welcome; I don't think I've said that yet.

I had to go look up the quote, and thought others might like an easy ref., so:

"The use of money is the purest act of faith; no anchorite who has followed a vision into the desert has acted on an idea as far-fetched as our belief that if we put a dollar in a machine we will be drinking a Diet Coke in a minute." Mary Gordon, We Are All Spendthrifts Now,
It is hard to tell exactly what she meant, even with this.
From the title, I might guess that perhaps she could have meant that anyone who spends money now is taking it on faith that there will be more money in the future.

Based on this quote, though, her logic is beyond me: we have MUCH evidence to support the belief that the machine will give us access to the drink we paid for.