With orders of $25 or more, Amazon offers the Mrs. Meyer's Clean Day 12.5-oz. Liquid Hand Soap 3-Pack in Lavender or Basil for $8.97. Clip the coupon the product page to drop it to $6.72. Plus, Prime members bag free shipping. (Non-members will need to spend $35 or more to qualify for free shipping.) That's $2.24/bottle and the lowest total price we could find for this quantity by $10, although three days ago we saw it for pennies less (and without the $25 minimum purchase requirement).
Note that this item is part of Amazon's "Add-on program"; it can only be purchased with an order of $25 or more. Also, the Basil version can be ordered at this price with an estimated in-stock date of December 7. Lavender may also require an extra one to two days to process.