MacMall offers the refurbished LaCie 20TB 5big Thunderbolt Series 5-Bay RAID Enclosure, model no. 9000398U, for $1,119.99 with free shipping. That's the lowest total price we could find by $679 for a new model. It features five hot-swappable drive bays with RAID 0, 1, and JBOD support, transfer speeds up to 785MB/s, and dual Thunderbolt ports with daisy chain capability.
Of note, no warranty information is included.