Amazon offers the Scotch-Brite 3M 4-Count Greener Clean Absorbent Scrub Sponge 6-Pack (24 sponges total) for $6.08. Check out via Subscribe & Save to drop it to $5.78 and bag free shipping. (You can get a similar quantity at Walmart for about 30 cents more via in-store pickup.) That's $0.24/sponge and about $33 under what you'd pay for the same quantity in local stores. These sponges are made with 23% recycled materials and from 100% plant-based fibers and are purported to outlast 30 rolls of paper towels.
Be sure to cancel your subscription once your order ships to avoid being billed for further shipments.