I’m fortunate that the stores I shop at display price per weight or volume for pretty much everything, but it varies a bit product to product in terms of what units they use.
Surely this isn’t a hard problem to solve, especially in Canada where you can just standardize on metric. Comparing price per 100g and kg is easy, just move the decimal place one. Comparing price per oz and lb is difficult, since you need to divide/multiply by 16, and that’s not easy to do with mental math.
Part of me thinks it’s malicious, but perhaps the simpler explanation is that these companies just don’t care.