I make it a habit to look for sales when I’m in the market to purchase a product, whether it’s groceries or a new string trimmer. In other words, I seek to pay less than the retail price. Imagine the opposite. That is, making it a habit to pay more than the retail price. It happens whenever a credit card purchase is not paid in full by the due date on the credit card invoice.
Here’s an example. If you purchase a product for $1000 using your credit card, but only make the minimum payments on the balance each month, the product priced at $1000 ends up costing you $1799! (This assumes a credit card interest rate of 18%.)
Take a look at the Credit Card Payment Calculator at this Service Canada site, and try out your own examples.
And consider this: If you are running a balance on your credit card (i.e., not paying in full each month), then the interest charges are applied at the point of every new purchase. A balance on your credit card eliminates the 25 day grace period for no interest charges.
Hazel Fluke, Financially Speaking 