For Prime members only, Amazon offers the Swiffer WetJet Extra Power Spray Mop Pad Refill 20-Pack for $8.40 with free shipping via the directions below. That's $4 under the price you'd expect to pay at your local store. To get this price:
  1. View the Swiffer WetJet Extra Power Spray Mop Pad Refill 20-Pack for $11.37
  2. clip the $3 off coupon on the product page
  3. order via Subscribe & Save for a final price of $8.40
Note: Remember to cancel you subscription after your order arrives to avoid being billed for subsequent purchases.