For its Prime members only, Amazon offers the Scotch-Brite 9-Count Non-Scratch Scrub Sponge 2-Pack (18 sponges total) for $11.99. Check out using Subscribe & Save to drop it to $11.39 and bag free shipping. That's $0.63/sponge, tied with our March mention, and about $5 under what you'd pay in local stores. These cellulose sponges can be sanitized in a dishwasher.
Be sure to cancel your subscription once your order ships to avoid being billed for further shipments.