Some of my thoughts.
Relic
Types: Treasure
Cost: $6
Worth $2. When you play this, you may trash up to 2 cards from your hand and play area. If you trashed at least one Action card, +$2 and +1 VP.
This can be a super Moneylender, but it's more versatile that Moneylender, And Counterfeit for that matter. Maybe it can use another bonus in lieu of the +vp bonus. I think vp tokens should be a bit more massable.
Usurer
Types: Action
Cost: $6
+1 Card. +1 Action. Reveal cards from your deck until you reveal a Treasure. Discard the rest. Trash the Treausre; gain a Treasure costing up to $3 more than it, putting it on top of your deck. Each other player may gain a Copper, putting it into his hand.
looks like a mine for next turn, but not quite. Mine (and Taxman) are terminal, but this isn't. Any cantrip can let you draw the treasure, including another Usurer. In fact, it might be too good at platinum flooding if you buy more usurers with the new treasure.
Treasure Chest
Types: Treasure
Cost: $4
Worth $1. When you play this, discard the top card of your deck. If it is a Treasure, gain a Silver
It doesn't get more thematic for the treasure chest expansion that this. Maybe better for another set, but still has my vote. Unfortunately, curses block the treasure gaining where the silver flooding might be most useful.
Metropolis
Types: Action
Cost: $7
+1 Card. +2 Actions. Treasure cards other than Copper produce an extra $1 this turn.
I hope this gets a "while in play" clause if it wins, but great concept I think. It's not quite Bank either. I like how it gives reward for having silvers, and gives reward for getting Kingdom treasures. Exactly what Prosperity can use. Too strong with the village effect?
Charity (A)
Types: Treasure
Cost: $7
Worth $4. +1 Buy.
While this is in play, when you buy a card, each other player gains a card costing at most $2 less than it.
With a "may gain" everyone gets Duchy when you get province and province when you get Colony. Or worse, causes a 3-pile when things just start coming together. Not so good. With a forced gain, it's practicaly GG if you pile out Pearl Diver or something.
Wedding
Types: Action
Cost: $7
+1 Action. Reveal cards from the top you your deck until you reveal an Action card, a Treasure card and a Victory card. If you do reveal a card of each of these types, put an Action card, a Treasure card and a Victory card from among the revealed cards into you hand. Discard the other revealed cards.
It seems pretty clear to me that the card refers to 3 distinct cards.
Cathedral
Types: Action
Cost: $7
Gain two action cards costing less than this and a Gold.
Should be more balanced with one action card gain. Good where Explorer is good. Even the most reliable engines might want gold to double province. Also good for BM-ish decks that just want 1 province a turn or something.
King's Greed
Types: Action
Cost: $10
Put your deck into your discard pile. Look through your discard pile and set aside up to 3 Action cards from it. Play them in any order.
Way too good, even at 10. This is one of those effects that just doesn't
lend itself to balance.
Mediator
Types: Action – Reaction
Cost: $3
+$3. Reveal 3 cards from your hand. The player to your left selects one of them. Discard it or put it on top of your deck.
When another player plays an Attack, you may set this aside from your hand. If you do, +1 Card, +1 VP, and at the start of your next turn, discard this.
Better than Mandarin, even if your opponent was the one who got to decide whether you discard or topdeck the card.
It can't give $3. The reaction wording is kind of weird. It should just be discard this from your hand, like Beggar.
Prospector
Types: Action
Cost: $4
+1 Buy. Reveal the top 4 cards of your deck. Put the revealed Treasure cards into your hand. Discard the rest. Each other player may discard a Treasure. If he does, he draws a card.
Aqueduct (A)
Types: Action
Cost: $7
+2 Buys. +$2. Reveal the top 4 cards of your deck. Put the revealed Treasure cards into your hand and discard the rest.
These cards are two versions of the same thing. If I had to pick one, I'd pick the more modest Prospector. That vault-like benefit to your opponents seems important to keep it from being a super envoy, though it might already be a super envoy.
Forum
Types: Action
Cost: $5
Draw until you have 6 cards in hand.
While this is in play, when you play a Silver, you may trash that Silver. If you do, +1 VP.
Again, I prefer having vp tokens be more accessible. It's all about being able to get 50+ vp tokens in a game. Nevertheless, I like the bottom effect that gives a benefit for trashing Silvers once they've outlived their usefulness
Dividends
Types: Treasure
Cost: $6
Worth $1. When you play this, gain a Treasure card costing less than this, putting it into your hand.
The presence of Venture in the kingdom would make this too strong. Otherwise it's kinda like Explorer and Masterpiece.
Hmmmm....
Inheritance
Types: Action
Cost: $5
+1 Buy.
While this is in play, Treasure cards costs $3 less, but not less than $0.
The treasure quarry. Simple, but nice. Quarry makes it look bad. It fits into BMU, but doesn't help buy
VP cards, so it would require some decision making.
Standard Bearer
Types: Action
Cost: $7
Trash this card. Put your deck (not including your discard pile) into your hand.
Needs a 10-card cap or something. Even then I'd be wary of this card. It's easy to trigger reshuffles with lots of cantrips and cheap sifters like warehouse and cellar. It might as well say draw everything. The extra swinginess isn't worth it in the end when it's a mega-turn enabler.
Charity (B)
Types: Treasure
Cost: $5
Worth $1. When you play this, choose one: Each player gains a Copper; or each player gains a Silver. Either way, put the card you gained into your hand.
Gravitates the entire game towards BM when players go for this.
Fountain
Types: Treasure
Cost: $6
Worth $0. When you play this, if you have no other Treasures in play, +2 VP. You may trash this immediately. If you do, +$2.
Probably my favourite vp token generator of the bunch. The anti-stack makes it work. The online version should add a line that says something like "ATTENTION, IT IS CRITICAL THAT YOU PLAY THIS BEFORE PLAYING ANY OTHER TREASURES"
Savant
Types: Action
Cost: $6
+3 Cards. +1 Action. Each other player draws a card, then reveals and discards one or more cards. He gets +1 VP per Action or Treasure card he discards.
Sort of like Governor, but I think I like this better. The vp chip penalty might be enough to make this cost $5. Does anyone else have thoughts about that?
Queen's Palace
Types: Action
Cost: $6
+1 Action.
You may return a VP token. If you do, +3 Cards, +1 Buy, and each other player gets +1 VP.
Setup: Each player gets +2 VP.
Never thought about trading in vp chips for stuff, but this implementation seems neat. Reminds me of The Traders and Barbarians scenario for Catan. That's a good thing for me.
Witch's Trove
Types: Treasure
Cost: $6
Worth $2. When you play this, reveal you hand and discard all revealed Curses. +$3 for each Curse discarded. You may gain a Curse.
Seems too heavy handed of a curse counter card, no?
Reputation
Types: Treasure
Cost: $10*
Worth $4.
Unless in play, this costs $2 less per card costing $6 or more you have in play, but not less than $0.
Grand Market can be a frustrating card due to it's strong snowball effect. This also has a powerful snowball effect, but maybe not as bad since it's a treasure and therefore anti-engine.
Indulgence
Types: Treasure
Cost: $5
Worth $2. +1 Buy. When you play this, the player to your left names a card in the Supply costing between $3 and $6. If you buy that card this turn, +2VP.
Also quite thematic for this treasure chest expansion. Maybe I will finally have a good reason to buy scout. You know what, this is really funky, in a good way. One of my favourites here.