Interesting video and it would make sense that it'd be hard to find any real tangible answer, but couldn't it just be that doubling anything that you're regularly exposed to just automatically seems like a large jump, because it is? (Conditioning is the term maybe?)
If you eat a single cheeseburger every single day for lunch and that's what you come to expect, one day having two cheeseburgers in front of you will seem like a lot, until you get used to it, then suddenly, two cheeseburgers seems normal. Then if you ate two cheeseburgers for lunch every day and one day are given four, suddenly that seems like a lot. Or if the reverse happens, and one day you're back to a cheeseburger a day, a single cheeseburger seems to be so little.