E Grand Mart via eBay continues to offer the Soundproofing Acoustic Panel 96-Pack for $79.98 with free shipping. That's tied with our January mention as the best per-unit price (83 cents) we've seen for panels like this and the lowest price we could find for a similar pack by $10. Each panel measures 12" x 12" x 1" and is designed to improve acoustics in recording studios, practice rooms, or home entertainment centers. Stocking up? you can also get a 192-Pack for $156.76 or a 288-Pack for $232.74, each with free shipping.
One grocery chain is likely to save you more money than any other.