Here is an example:

Jason is at a used car lot, talking to a saleswoman.

Jason: "What's the top speed on this $300,000 Ferrari, compared to that $30,000 Ford?"

Saleswoman: "The Ford tops out at 120 mph, but the Ferrari can do 180 mph easily."

Jason: "Well, it only goes 50% faster, so it should only cost 50% more. I'll pay you $45,000 for it."

Jason is comparing the two cars just on the basis of top speed, and expecting that to be the only basis of comparing their relative value. But the Ferrari differs also in handling, acceleration, styling, luxury, and rarity. The basis of Jason's comparison is therefore highly questionable.