Do Legendary skins ever go on sale?
Solution 1:
No. Legendary Skins will never go on sale, and have not done so in the past. While I can't find the original official statement at the moment, the forums reassert this every few days when someone asks.
It is part of their essence in addition to their exorbitant prices. They're meant for people who are willing to fork over that much just to see their little adorable Void creature spew pretty fireworks.