With orders of $25 of more, Amazon offers Prime members the Nerf Super Soaker Microburst 2 Blaster for $4.99 with free shipping. (Non-members can spend $35 to bag free shipping.) That's the lowest total price we could find by $3. It holds 10 ounces and has a 33-foot range.
Note that this item is part of Amazon's add-on program and can only be purchased with an order of $25 or more.