Make it cost a lot of tokens, like somewhere around 20-40m tokens per keyThat would make crystal keys way less rare and make it possible for people to get more Legendary crystals making those less rare. And you can only get crystal keys from voting and the Vexed kit not the vote or prestige crates. Also considering some people make a lot of tokens, it wouldn't be wise to make them buyable with tokens in my opinion.
People could use their 'token pickaxes' to get many Crystal crates ; gets them either alot of crystals they could sell, or Legendary crystals that they could use to make more tokens, which in return get them more keysThat would make crystal keys way less rare and make it possible for people to get more Legendary crystals making those less rare.