A penny saved is a penny earned. - Poor Richard
When Benjamin Franklin penned those words, income tax was not the law of the land. Today, a penny saved is worth much, much more than a penny earned.
When we earn a penny (or a dollar, a mark, a yen, etc.), we are obliged by a variety of national and local laws to pay a fraction to income taxes. This can range from around 13% to much higher percentages depending on your income tax bracket. On top of that basic tax, there are usually a number of social taxes: national pensions, unemployment insurance deductions, etc. Then there are benefit deductions for a variety of items: insurances, pension or retirement savings plans, union dues, donations, etc.
By the time all the deductions have been removed (not to mention the personal costs of earning that money -- commuting, clothing), our earned penny has shrunk by one third or more. Finally, when we go to make that purchase, sales taxes and/or goods-and-services taxes take another bit from our penny. By the time the assualt is over, we likely will have to earn two pennies to purchase one penny's worth of goods or services.
A penny earned is not worth a penny at the store. And we had to work hard to get that penny. Saving a penny is saving a penny: period. And we don't usually have to work as hard to save as we do to earn. Common sense alone can save that penny.
Sorry, Ben, we have ruined your math. But then, you did tell us to save that penny.