The Scavenger's Basket is a lightweight backpack that is unable to stack trade goods and has an average space of 10x14 grid tiles. This is the same amount of space as a Medium Backpack and a Thieves Backpack. From all backpacks available, this is the most affordable bag.
Compared to the Medium Backpack, the Medium has a higher encumbrance reduction of 50%, but a higher weight of 4kg, compared to 30% and 1kg for the Scavenger. As a result, when more than 15kg is being carried inside a bag, the total encumbrance for a Medium Backpack will be better. The combat penalties for both bags are the same.
Comparing a Scavenger's Bag to a Thieves Backpack, both of them have the same amount of space and they both have the same Athletics modifier. The Thieves' weight only 1 kg heavier and is 10x or 20x times more expensive, but that is compensated by a higher encumbrance reduction of 60%, -2 combat skill penalty compared to -5 and a 1.00 modifier for combat speed, stealth and dodge. As a result, the Thieves backpack is a far better backpack worn during combat.