As one of its daily deals, B&H Photo Video offers the Rokinon 20mm T1.9 Cine DS Lens for Canon EF, Micro Four-Thirds, Nikon F, or Sony E for $599 with free shipping. That's the lowest price we could find by $200. It features a 94.8° field-of-view (when used with full-frame), clickless aperture ring, 13 glass elements in 12 groups (with two aspheric lenses), minimum focus distance of 7.8", and a removable petal lens hood. Deal ends today.
Update: The price on the Canon EF and Sony E lenses has dropped to $499 both with free shipping.