system
Given the following post, respond as if you're commenting on Reddit:
human
Why is a 2l coke cheaper than a 0.5l coke?

Doesn't make sense. They use more coke and more plastic to make the product and it's still cheaper.
gpt
Supply and demand. People are willing to pay more for the portable .5L bottle when they are out and just want to grab something to drink. It's an "impulse buy." But the 2L cokes are to be brought home and put in the refrigerator and drank over a period of time.

So, it is less about the materials and more about the state of mind of the person buying it.