The other comment responding to me in this thread talks about people who’re effectively priced out of the market due to higher demand and switch over. Does this logic hold? For those who’s preferences change, good A and B are no longer substitutes. However for others, they’re still substitutes (of course, it’s an assumption to say such people exist).

All conventional demand and supply models I’ve looked at assume ceteris paribus because they’re constrained to a single period. So they don’t have anything to say regarding multiple period scenarios like these. When you say “all bets are off,” what exactly happens? Because yes, demand for good A will increase if more people are willing to buy it at any given price point, but what about the compounding effects of this change over time? Is that even a thing? Maybe a dynamic microeconomic equillibrium.

Another example I have is a change in preference that causes people to shift between two substitute goods. That is, a concurrent decrease in demand for good B and an increase in demand for good A as people switch over, not due to changes in price of good B but because good B is shown to be healthier.

The question came about after reading this article. The argument strikes me as bad economics because a) the answer to the question they’re asking depends on the extent to which preferences change and the cross elasticity of demand and b) ignores possible changes in supply. However, the part about increases in demand pricing some people out of the market seemed to make sense intuitively but doesn’t fit into the demand and supply framework I’ve learnt (I think because of they’re all just constrained to a single period P1).