Crux Chests should be attained just as Inferno and Aqua are. They should be kept as an item dropped with the same rarity as Aqua/Inferno. The harder the Epic Battle decides whether it's the golden Crux Chest or the normal.
Tr1 spent over 3 k on the gold and silver ones on blk friday. I told him he was stupid because even though they say for a limited time on sale they will always be available through their events so they make u spend money on xstals. Seems he spent his money well