Not really; there are differences between the two - a price differential is something that could possibly be checked, reasonably objective fact that inferences

Not really; there are differences between the two - a price differential is something that could possibly be checked, reasonably objective fact that inferences can be drawn from. Someone's weekly supermarket choices are not fixed like the cost-of-living index basket of goods, they are entirely subjective and will change, sometimes hugely, from week to week without anything needing to alter in the world economy, and the fact that a bill is reported as being higher does not allow me to make useful predictions.