Currency to open them is of course Treasure Maps (one, ten, or fifty at a time.)
Each chest contains one of the possible resource types obtainable from playing Treasure Maps.
Size of each reward and comparative likelihood of each reward scaled so that the expected return over large number of chests is equal to the expected return of playing a Treasure Map (averaged across all players), multiplied by a fraction.
Fraction TBD of course. I’d be fine with 1/3. Needs to be on the low end because this would be a new “opportunity cost” expense of actually playing Treasure Maps. ie instead of playing for 10 minutes to get the full value of a TM, you’d now be playing for 10 minutes to raise the return you get from a TM from 1/3 to full.
Interesting idea but I’d rather any effort went into making TH more fun… This would be like conceding defeat that many (higher level) players have given up on it…
Well I don’t see it that way. The little map symbol that appears when you get a long chain is meant to be a bit of ooh yay, aka fun. But right now it’s meaningless if you’re not a map-player.
If they’re making a new minigame that costs maps to play, all the better.
Personally, I would rather they introduce a feature that just multiplies the earnings from a single map. In my head, each two maps spent increases the multiplier by one.
There is plenty of space on the UI of the current treasure maps screen for such a counter, as opposed to the current chest screen which is kind of crowded.
Edit: different players play to different ends. I try to keep green chests on the board as much as possible because I want to earn gems. On the other hand, lots of people push all the way to vaults. A chest that gives expected earnings based on all players will give a different result from what I would average over 50-60 maps.