For Prime members only, Amazon offers the Zwipes Microfiber Cleaning Cloth 24-Pack for $9.88. Order via Subscribe & Save to cut it to $8.40. With free shipping, that's tied with our March mention and the lowest price we could find by a buck. These 12x16" cloths purportedly absorb eight times their own weight.
Be sure to cancel Subscribe & Save once your order ships, or you'll be billed for subsequent shipments.