I have heard people who grew up in the 1930's, or earlier, refer to their inability to afford Coke as a way of describing their poverty or their sudden decline in wealth.
Was Coke ever an expensive, sought after treat associated with wealth? Was there some reason that people would choose to use Coke as the reference point when describing their class?
Not necessarily. In fact, the opposite may be true. Coke was never a particularly expensive drink in those times. Even into the 1950s, Coke was typically 5ยข a bottle. Being able to afford to buy Coke may speak to the person coming out of abject poverty, and being able to afford to buy even something as relatively insignificant as a soda. On the flip side, the opposite may be true: people who were lower-class were suddenly plunged into poverty so bad that they couldn't afford Coke anymore.