MacMall offers the Wenger Swissgear Upload Carrying Case Backpack in Black, model no. GA-64081001, for $17.99 plus $6.29 for shipping. That's the lowest total price we could find by $3, although we saw it for $2 less last month. It features a carrying handle, multiple compartments, and room for up to a 16" laptop.
Retailers mark up products by hundreds of times their cost — but you don't have to pay the premium.