Home Depot has the Mr. Clean Magic Eraser (single pack) advertised on sale for $1. You can use the $1/1 coupon from the Home Made Simple book (if you requested it and received it) to get these for FREE! There is also a $0.50/1 coupon from the 8/28 PG or a $0.75/1 coupon from the Organize in Style book!
These would be great to donate to schools if you don't need them personally!
You can always price match at Target or Walmart too!