There's some legitimacy to the substitution approach, because people do e.g. switch from hamburger to chicken when the former gets more expensive (steak, if it was substituted by hamburger, is fraud), and at least this is a special case of production issues vs. something driven by "secular" inflation (drought really wacked cattle production, as my father's friends who raised them attested at the time).

But it's easy to take too far, and any consumer who nonetheless insist on having some steaks, or more expensive hamburger, you'll not be impressed by this statistical substitution trick.