Kids want five pennies rather than one nickel because five is more than one and research suggests that we don't outgrow that mentality as we age.  Check it out. 

Researchers at Virginia Tech say that there are pricing tricks that retailers use to get us to buy more than we need and we have no way to stop it.

Our brains respond more to a sale that says "50 items for just $29" rather than "$29 for 50 items" because we see a large quantity first and it's almost twice the items than the price and it's difficult for us to resist.

The University of Michigan found that when products such as car batteries are advertised, we prefer to hear sales points like battery life told in minutes. Rather than "two hours of battery life" we want to hear "120 minutes of battery life" because it's a big number and we like that, even though we really should know better.

We really should.