Cost reduction is a recurring mechanic in Dominion. Rather than directly fielding coin, cost-reducers decrease the cost of cards, an effect which becomes more valuable with more buys. Typical cost reduction instructions follow this wording:
- [All cards or some subset of cards] (including cards in players' hands) cost less this turn, but not less than .
However, with the 2019 errata, the "but not less than " clause has been dropped, as it is now a general rule that costs can never drop below , and that clause was never included in any of the cards of this type in Menagerie.
List of cost-reducers
- Bridge - the archetypal cost-reducer
- Quarry - reduces Action cards by
- Princess - reduces costs by , but only one copy
- Highway - cantrip
- Bridge Troll - durational cost-reducer
- Ferry - reduces a single Supply pile's cost by
- Inventor - gains a card costing up to before its cost reduction kicks in
- Canal - reduces costs on your turn for the rest of the game
List of cards whose own price can be reduced
There are currently five cards whose cost is variable. These have a base price which can be changed by something that happens during your turn. Of these, four are in the Menagerie expansion
- Peddler - cost is reduced by per Action card in play, but only during your buy phase
- Animal Fair - can be gained for no during your buy phase, by sacrificing another Action card
- Destrier - cost is reduced by the number of cards you gained on that same turn
- Fisherman - cost is reduced by if you have no cards in your discard pile
- Wayfarer - cost is equal to the cost of the last-gained card, and can even become more expensive than its base price
Most cards that reference a specific cost in Workshop can gain any card costing up to ; without cost reduction, this effect is rather weak, but with four Highways in play, a Workshop can gain Provinces. On the other hand, cards that give a scaling effect per cost in of another card (most often trash for benefit cards) will do less well with cost-reducers, as their effect will be diminished, and cards that reference a cheaper card will give no effect if their cost has been reduced to . For examples, trashing a Silver to an Apprentice when you have Princess in play will only draw you one card, and with five Highways in play, Band of Misfits can't do anything.do well with cost-reducers, as most such cards use the specific cost as an upper limit. For example,
Since cost reduction affects cards but not Events, it is less useful for strategies that depend heavily on buying Events (or Projects).