Have you ever bought something only to have it go on sale the next week? Now there’s a service – Paribus – that automatically gets you a refund on the price difference at 18 different online retailers including Amazon, Macy’s and Target. Paribus is insurance that you’ll always get the best price, even when retailers like Amazon change their prices 100 million times each day.  And the best part?  It’s totally free to sign up. Paribus only charges 2% of the refund amount AFTER they’ve secured your cash back.  So you get 98% for doing nothing.