Originally Posted by
mike_s
So, if I find a Ferrari on sale for $400,000 instead of $500,000, I'll be $100,000 richer if I buy it!
It depends. If you had a choice to buy it or not your logic would hold, and finding it on sale wouldn't effect your wealth.
But if you had to buy a Ferrari, possibly because you had a contract to sell one at a set price, finding it for $100,000 less would make most definitely you richer by $100,000.
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Go back to my earlier tug of war strategy. A goat is tied in the middle of a rope with two people pulling at the opposite ends. As long as they both pull equally the goat won't feel a thing. If either suddenly gives a harder tug, the goat will be pulled in that direction. I'm sure you accept that. After all, as you said, it's common sense.
Now if one person suddenly relaxes his pull what happens? The goat will be pulled in the opposite direction by a force exactly equal to that reduction in force by that person. it's a simple balancing process,
reducing the force in one direction is functionally equal to increasing the force in the opposite.
Kids learn this by experience because it works in tug of war, on seesaws, or others things they deal with. Then they become adults, learn a little bit and can no longer accept what doesn't fit into their narrowed view of how things work. But the physics doesn't change.