Formula for translating a card from cost X to cost Y1. Add "-1 Card, -1 Action" to the card.
1a. If the card is weak for its price, maybe throw in a +$0.2 or so. If strong, maybe a -$0.2.
2. Multiply all effects on the card by C[X,Y].
3. Add "+1 Card, +1 Action" to the card.
4. Tweak the card to make the numbers round, keeping the power level about the same, and keeping the spirit similar to the original.
4a. In particular if the original card granted 0, 1, or 2+ Actions, make the new card grant 0, 1, or 2+ Actions as part of the tweak.
C[3,6] ~= 2.3
C[4,7] ~= 4
C[3,9] ~= 5
C[Y,X] ~= 1/C[X,Y]
Notes:
1. The empty card is an Action whose printed effect is +1 Card, +1 Action. A card's effects will now refer to the difference in game state after you play that card from the game state after you played the empty card instead. So the effects of a Smithy are +2 Cards, -1 Action.
2. 3-cost and 4-cost cards have roughly equal value, with 4-cost cards generally being a little more powerful but not much. 5-cost cards are significantly more powerful than 4-cost. 6-cost cards are decently more powerful than 5-cost, and 7-cost decently more powerful than 6-cost. 2-cost cards are generally weaker than 3-cost, but may be priced at 2 for availability rather than power level considerations.
3. Card effects can be roughly evaluated in a vacuum. That vacuum will be essentially Big Money. We could use other vacuums and get somewhat different results.
4. Some cards are actually net negative to add to your deck on average (aka in a Big Money vacuum). These will not transform well now, but may transform well with a different vacuum assumption.
Silver
$3 - Action
(cantrip)
-1 Card
+$2
We can make this stronger or weaker by multiplying its effect by some factor. In general +Card on a non-terminal is a bit better than +$, so Silver has a net effect of around +$0.75ish. Gold is around +$1.75ish, so the factor was around x2.3. Definitely more than x2, definitely less than x3. Platinum is around +$3.75ish, or x5. Let's apply a x2.3 multiplier to another 3-cost...
Super Warehouse
$6 - Action
+6 Cards
+1 Action
Discard 7 cards.
This comes out to be basically a somewhat better version of playing two Warehouses in a row, which makes intuitive sense.
Super Chancellor
$6 - Action
+$3
You may put your deck into your discard pile.
Multiplying a weak card gives you a weak card.
Super Fishing Village
$6 - Action
Put a card from your hand on top of your deck.
+3 Actions
+$2
At the start of your next turn, +3 Actions, +$2
Multiplying a very strong card gives you a way-too-strong card. One way of gauging power level might be to apply a transform to a price point far away and see if the resulting card is far under or over powered. For example, let's take a look at a transform from 4-cost to 7-cost and then apply it to Jack. King's Court versus Throne Room?
Throne Room
$4 - Action
(cantrip)
-1 Card
+1 Card that is a copy of an Action you totally already have in your hand
Add "+1 Action" to the Action you just drew
---
There's some chance you're not allowed to play this card.
King's Court
$7 - Action
(cantrip)
-1 Card
+2 Cards that are both copies of an Action you totally already have in your hand
Add "+1 Action" to each Action you just drew
---
There's some chance you're not allowed to play this card.
Getting a new card is good but this card is way better than +1 Card since it's something you bought and thus very likely better than your average card. How much better? Well, maybe your average card has an effect of around -1 Card, +$1.2, but your TR/KC-able cards are on average -1 Card, +$2.2, making drawing a TR/KC-able card worth around 2x +1 Card.
KC: +2 Actions, +2*2-1=+3 Cards, maybe you can't play this
TR: +1 Action, +1*2-1=+1 Card, maybe you can't play this
KC/TR ~= 3.3ish cards / 0.8ish cards = x4
Now let's create a 7-cost card out of an average 4 and see if it's reasonable, then if it is, let's create a 7-cost card out of a strong 4 like Jack and confirm that it's unreasonably strong.
Super Farming Village
$7 - Action
+3 Cards
+5 Actions
Discard 2 cards
That's quite strong... but maybe reasonable for a 7-cost.
Super Jack of All Trades
$7 - Action
Gain 4 Silvers
Reveal the top 4 cards of your deck, you may discard any of them and put the rest back in any order
Draw up to 6 cards in hand
You may trash up to 4 cards from your hand that are not Treasures
This shows a weakness in multiplying things by 4... I had to kind of fudge bits to end up with a sensical card, like canceling some -Cards and -Actions with some "draw up to 5 again and again", and discounting the value of trashing up to 4 non-Treasure cards. Also, if multiplying "gain a Silver" by 4 turned into something slightly worse than "gain 2 Golds" rather than turning into "gain 4 Silvers" then SJoAT would work quite well in a Colony game... as is, it probably doesn't so much. It feels weaker than I expected... but in reality my valuation of it probably suffers from the same thing our initial valuation of Jack suffered from, and SJoAT is super-strong.
Hmm, Trusty Steed comparison? Oh. This is way better than Trusty Steed. Yep, strong.
For funsies, let's divide Province by 5ish. We should get a weak 3, since Platinum divided by 5 gives us an average 3.
Cruddy Province
$3 - Action-Victory
+0.8 Cards
+1 Action
Worth 1.2 VPs
Hey look, Great Hall. Maybe by downgrading a unique high-cost card we can get a unique low-cost card. Hoard divided by 2.3?
Cruddy Hoard
$3 - Action
+1 Card
+1 Action
+$1
Discard a card.
When you buy a Victory card this turn, gain a Silver.
Not bad! Translating fractional effects was hard on this one, though... I basically equated (+$0.1, -half the difficulty of buying a Victory rather than just any card as a trigger) to (+0.45 Cards, discard a card). Probably similar but not quite formulaic... this is strictly better than Oasis, but Oasis is a bit weak, so maybe this is still a $3. Plus I kind of made up 1.75ish/0.75ish = 2.3x to get the multiplier, so maybe it needs to be closer to 2.5x to get from 3-cost to 6-cost.
Maybe also we can price cards by noticing that some multiple of the effects gives something similar to an existing card? Let's check the Mini-Set winners? Thanksgiving... Trash, gain two cards costing up to a total of 7, putting them on your deck. Sounds like Feast.
Thanksgiving
$? - Action
(cantrip)
-1 Card
-1 Action
Trash this.
Gain a card costing up to 5.
Gain a card costing up to 7 minus the cost of the card you just gained.
Put those two cards on your deck.
Feast
$4 - Action
(cantrip)
-1 Card
-1 Action
Trash this.
Gain a card costing up to 5.
So Thanksgiving gives you a possibly much better card (up to twice as good!) and a poor card, with the option to gain two engine pieces instead or something, and gives you half an additional play of those cards, ish. Thanksgiving makes you trash twice as much goodness as Feast. It doesn't make you lose twice as many cards or actions. It sounds like it's around 2 times as good as Feast. It's clearly not 3+ times as good, but it's clearly much better than exactly as good, so that puts it squarely at $5. (Where it already was.)
