Comment by lblume

The cheapness is due to the prevalence, and the prevalence of sugar caused sweetness receptors to be evolutionarily advantageous. There is no world in which sugar is extremely expensive, markets still function basically in the way they do now and humans experience the sensation of sweetness the way they typically do now. Cocaine and other types of "hard" drugs are qualitatively different in that regard.

Your example also doesn't really hold up because people typically don't process cocaine in the way they do with sugar and other carbohydrates. In your hypothetical scenario, we might see people consuming large amounts of pure sugar (or artificial sweeteners), but they wouldn't go to lengths of baking bread using it.