A couple weeks ago, Amazon announced a special deal: $8 and some change off any order of $50 or more. Pretty good — over 16% off. But be careful. If you’re trying to use money efficiently, then you need to remember that when you use a coupon you only save money if you buy something you were going to buy anyway (and of course, the Amazon price has to be as good as or better than price you normally pay).
I used the promo deal to buy the same kind of snacks I usually buy by the box to keep at work, thus avoiding buying anything from a vending machine. Because the Amazon price was comparable to the usual price, I’ll save 16% over the time it takes me to consume the snacks. Given that “a penny saved is a penny earned”, I’ve earned over $8. Is there any other way to earn $8 on a $50 investment in just a few weeks, with 100% certainty? No, there isn’t.
But what if I had used the promo code to buy something I just wanted, but didn’t really need. Say, a fancy new shirt … when I have already have plenty of shirts, probably all I need for the next few years. (And, I often get new ones for birthday or Christmas.) If I had bought a new shirt for $50 and used the promo code coupon to reduce the price to $42, wouldn’t I have saved $8? No. Using the promo to buy a new shirt I didn’t need would not have been a savings of $8 — it would have been an expenditure of $42.