I didn't claim the law of demand was perfect or that substitute goods don't exist. I was merely pointing out that wisty was wrong to claim the law of demand requires that "a huge number of axioms hold (none of which are true)." You need only one axiom which is, generally speaking, reasonably accurate.
Further, your example of jeans is trivially explained by noting that "jeans" is a broad category of goods, not a good itself. I.e., there is one demand curve for Levi jeans, a separate demand curve for hipster jeans, and a third demand curve for genuine levi jeans (not jeans that appear at first glance to be Levi, but sold by a shady discount store).
Your critique of the demand curve for jeans applies much better to various demand aggregates in macroeconomics, not the law of demand for specific goods.
Further, your example of jeans is trivially explained by noting that "jeans" is a broad category of goods, not a good itself. I.e., there is one demand curve for Levi jeans, a separate demand curve for hipster jeans, and a third demand curve for genuine levi jeans (not jeans that appear at first glance to be Levi, but sold by a shady discount store).
Your critique of the demand curve for jeans applies much better to various demand aggregates in macroeconomics, not the law of demand for specific goods.