This concept might make more sense if the roles were reversed. Let’s play devil’s advocate for a moment, where you are the shipper. To further simplify this idea, let’s make all shipping costs equal, no matter which method (air, land, or sea). Knowing that there’s a numerical limitation in weight and space on any given solution; land, air, or sea. Which is more important, the weight or the volume? In truth, this depends on how you, the shipping carrier, decide to charge. This is called the chargeable weight. Many of the major shipping carriers charge depending on whichever weight is greater. If the package dimension weight is greater, they will charge by dimensional weight, and if the weight is greater, they will charge by the actual weight. Whichever is greater, will be the billable weight.
For example, let’s say that there are two sellers, one who sells pillows, and the other selling mobile phones. Would you charge the pillow vendor the same amount as you would charge the cell phone vendor? The phones use less space (volume), but weigh more. In contrast, the pillows have less weight but much more volume. To think of it another way, one pound of cotton vs 1 pound of iron. You might think that the one pound iron would cost more, but in logistical terms, the cotton is more costly. Why? It’s because the name of the game is optimization. Calculating the most effective way to optimize the space available in whichever shipping methods the client chooses.