Only a chocoholic would relate to munching from two different packs of M&M's at a time.
Let's assume that one was a pack of standard M&M milk chocolate and the other was a pack of M&M peanut butter chocolate.
While most of the people would get lost in their M&M's, only a keen observer would find something strange.
When you look closely at the packaging, you'll notice that both the packs cost $1, but the pack of peanut butter M&M's weighs a tiny amount less. 0.06 ounces(1.7 grams) less to be precise.
The first thought that would come to your head would be - the peanut butter M&M's might just be slightly more expensive to produce. Mars, the company that makes M&M's, must be adding a lesser quantity of the peanut butter M&M's per pack to keep their profit margins intact.
But that's incorrect. In fact, peanut butter is usually less expensive than chocolate, so logically you should be getting more peanut butter M&M's per pack than milk chocolate M&M's per pack.
The next thought you'd have is that maybe the machines at the factory fill every M&M pack with a fixed number of M&M's. For example, this could mean each pack is always filled with 10 M&Ms irrespective of what kind of M&M it is. If the peanut butter M&M's were lighter than the milk chocolate M&M's then the peanut butter M&M pack would be lighter, since they both have the same number of M&M's.
This would also be incorrect since peanut butter M&M's actually weight more than the milk chocolate M&M.
The answer has nothing to do with the price of peanuts against the price of chocolate or the number of M&M's in a pack.
What really matters is the number of CALORIES!
Look closely at both the packs shown in the picture. The factor that is of real importance is the number of calories. If you add just one more peanut butter M&M into the pack, the caloric value of the entire pack would shoot above 250 calories.
This magic number of 250 calories is something the candy companies do not want to cross since they would then be entering the territory of a burger, pizza or even a small meal.
Mars knows that M&M is a snack. A few years back the number of calories in a snack might not have been as critical as the snack's price, taste or quantity but things have changed. In today's world where consumers are getting more health-conscious and cutting down sugar, it is extremely important for all snack companies to recognize this shift and align their products accordingly.