When shopping online, it can be difficult to compare prices between similar products because they come in slightly different size containers — or to see if you’re really getting a good deal by buying in bulk — because many e-tail websites don’t include unit pricing to tell you many dollars per ounce/gram/liter or other standard unit of measure. But today, some of the biggest names in retail agreed to start listing unit prices, while the biggest name in online shopping won’t commit. [More]