I have two separate suggestions to decrease shadow key price and calm down the audience to some extent, making both $$ for developer and more afford-able experience for players.

First suggestion: I offer to give one shadow key to each player who buys $10 or more CE. Same as with regalia pieces. This will fix the main problem - shadow key price. Since reward isn't worth it (those new armors offer exactly same amount of protection as others, it may be a different combination, but the amount's the same), its the new "experience" people are after. Why not just give it to them? Give people keys as you gave them rose regalia pieces. This way key's price will drop to around 2-3k CE, 500-750 ce per team member who wants to go inside. Relatively affordable.

Second suggestion: make keys not vanish immediately, but have a specific amount of uses. Learned on example of Team Fortress 2, where dueling mini-game has 5 uses, sound-making item has 25 uses. I believe its a good business model - making items that are used up during playing. Its much better than "permanent" keys and "permanent" armors because you don't need to pay for it more than once.
First consume-able objects were keys and accessories (which are destroyed upon being detached from armor), now keys follow suit. But why 1 use-keys? They're extremely expensive, so make them 4-uses or 5-uses keys instead. This will keep key price at current level but make runs more affordable for the team - run once and sell the key so others can make a run and so on.

If you agree with either of these suggestions, just bump the topic :)
Me I got a whole of 4 rose regalia sets while the last even went on, 9 pieces total.

Bonus suggestion: add bragging rights to artifacts. Like, small medals that show when you inspect someone. For example, a medal for each boss and a medal for bought CE packs. They need to look good and make me jealous so I'd want to have them.

PS: still don't understand why is a young player trying to each old developer new tricks... at the same time I see these tricks sometimes being heard - last bug report about kleptolisks(?) stealing 3 health capsules and returning only 1 after being killed had its effect - in the latest patch they fixed this bug, now those little beasts only steal 1 item instead of a whole slot (they emptied a whole slot, regardless of amount of items, always returned only 1 item). Now, if the game would stop "relocating" me into traps...