Understanding the value of a dollar is probably the most important thing anyone can learn about money.
Here it is - plain and simple.
When you next go and buy something, think about how long it took you to earn each dollar. Then when you go to buy something, calculate how long it took you to earn those dollars to buy that product.
For example - after-tax, you earn $10 an hour. If you go and buy a T-shirt for $30. Is that T-shirt worth 3 hours of your time? What else could you have bought with that $30? If you want to buy something else, you are going to have to earn more money.
Was that T-shirt worth your time?