Adorama offers the Pentax DA 16-50mm f/2.8 SDM Lens in Silver, model no. 21650, for $699 with free shipping. That's the lowest total price we could find by $9, outside the mention below. This lens features a 24-75mm focal length, bright constant f/2.8 maximum aperture, quick-shift focus system, and super protect coating.

A close price, B&H Photo Video has it for $699.95 with free shipping.

Update: The price at B&H Photo Video has dropped to $683.95 with free shipping.