AmericanWholesale via Amazon offers the Aveeno Clear Complexion Cleansing Bar
for $3.27 plus $1.99 for shipping. That's the lowest total price we could find by a buck. This 3.5-oz. cleansing bar contains soy and salicylic acid.
Update: It's available via this link for $2.73 plus $1.99 for shipping.