Walmart offers the Greenco 5-Tier Wall Mount Corner Shelves in Walnut for $19.99. Choose in-store pickup to avoid the $5.99 shipping fee. (Amazon charges the same with free shipping for Prime members.) That's tied with our mention from ten days ago and the lowest price we could find by $6. It measures 7.75" x 7.75" x 48.5" and includes all necessary mounting hardware.

Update: Pickup is no longer available at Walmart. Amazon still offers it for $19.99 with free shipping for Prime members.