Staples offers the Staples Cap Erasers 12-Pack in Assorted Colors for 99 cents. Plus, Staples Rewards members qualify for free shipping. (Not a member? Click here to sign up for free.) That's the lowest total shipped price we could find by $1.
Of note, Staples also offers this 12-pack in Pink for 96 cents, but only with orders of $50 or more.