There’s a heuristic at work here which isn’t completely unreasonable.
I buy $15 items on a daily basis. If I form a habit of ignoring a $5 savings on such purchases, I’ll be wasting a significant fraction of my income. I buy $125 items rarely enough that I can give myself permission to splurge and avoid the drive across town.
The percentage does matter—it’s a proxy for the rate at which the savings add up.
It’s also a proxy for the importance of the savings relative to other considerations, which are often proportional to the value of what you’re buying. If you were about to sign the papers on a $20000 car purchase, would you walk away at the last minute if you found out that an identical car was available from another dealer for $19995? Would you try to explicitly weigh the $5 against intangibles such as your level of trust in the first dealer compared to the second, or would you be right to regard the $5 as a distraction and ignore it?
Poor kid. He’s a smart 12 year old who has some silly ideas, as smart 12 year olds often do, and now he’ll never be able to live them down because some reporter wrote a fluff piece about him. Hopefully he’ll grow up to be embarrassed by this, instead of turning into a crank.
His theories as quoted in the article don’t seem to be very coherent—I can’t even tell if he’s using the term “big bang” to mean the origin of the universe or a nova—so I don’t think there’s much of a claim to be evaluated here.
Of course, it’s very possible that the reporter butchered the quote. It’s a human interest article and it’s painfully obvious that the reporter parsed every word out of the kid’s mouth as science-as-attire, with no attempt to understand the content.