There is no existing drive upgrade Promo currently in place. You would have to purchase a new 1U with the largest available drives (6TB), but it would be discounted when you return the old 1U with smaller drives. Obviously, you would need to keep the old 1U to Replicate your content before returning it to K, so K collects a deposit on that 1U from your dealer, and this is returned after K confirms receipt of the returned 1U. There are conditions that must be met in order to get the deposit back (basically 1U must be in working order and in reasonably good cosmetic condition. Your dealer can explain more.)
K's not trying to "price out" the Premiere line, the higher cost is partly based on the fact that you now have to buy the new Server, not just the drives (it's been like this for quite awhile and is not related to the recent temporary shutdown). Your dealer also determines the actual cost to you, so that can be a factor as well.
Jim