What a cost curve is
In a card game or a strategy game, nearly everything you can field has a price: mana, energy, supply, gold, action points. A cost curve is the relationship between that price and what you get for it. Plotted on a graph, price runs along one axis and power along the other, and the designer’s job is to keep every card or unit close to the line.
The idea is not that all options are the same. It is that, for a given price, no option should be clearly better than the rest unless there is a reason, such as a drawback, a condition or an extra requirement. When a card sits well above the line, players tend to include it everywhere. When it sits well below, nobody uses it.
Building a baseline
Designers usually start with the simplest objects: plain creatures or units with only stats. A common approach is to set a rule of thumb, such as a fixed amount of total stats per point of cost, and then test it.
A worked example, with invented numbers: suppose a plain creature gets 2 points of total attack and health for each point of cost, plus 1 free point. A 1-cost creature then has 3 total stats, a 2-cost creature has 5, and a 3-cost creature has 7. The formula is 2 times the cost plus 1.
Now add an ability. If a designer decides a “draw a card” effect is worth about 2 stat points, a 3-cost creature with that ability would have 7 minus 2, which is 5 stats. A drawback works the other way: a creature that cannot block might receive a bonus of 1 or 2 stats.
The values are only estimates, and different designers disagree about them. The point of the exercise is to put every option in a common unit so that comparisons are possible.
Why the curve is not a straight line
If the world were linear, a 6-cost card would simply be six 1-cost cards combined. In practice that is not true, and designers deliberately bend the curve.
Tempo. Players only have so much to spend each turn. A 6-cost card uses most or all of a turn on one object. Because the mana curve limits what fits into one turn, the cheap option can often be played alongside others, which is an advantage the expensive one must pay for.
Concentration. One big unit can be removed by one cheap effect, while several small units cannot. A big unit therefore needs a bonus to offset the risk.
Stacking. Two small units together may produce combined effects that a single big one cannot. This is why designers often charge more per stat for efficient early cards than for late ones, or the reverse, depending on what the game is trying to encourage.
Availability. Players cannot play a 7-cost card until they have enough resources, so expensive cards are dead in hand early on. Their power per point is usually higher to compensate for waiting, often described as paying for the delay.
Abilities that break the formula
Some effects do not fit neatly into a stat budget. Examples include:
- Effects that scale with the board, such as “gain +1 for each other unit.”
- Effects that give a player more resources, which can break the whole economy if priced too low.
- Removal, which is worth different amounts depending on what it hits.
- Combinations with other cards, which are hard to price in isolation.
For these, designers rely on playtests and win rate data rather than formulas. A card whose win rate is far above average at a given price is a candidate for adjustment through balance patches. This ties to a broader approach to win rate balance, in which numbers from real play correct what the model got wrong.
Cost curves beyond cards
The same thinking applies in real-time strategy units, tactical RPG classes and auto-battler pieces. A fast cheap unit that gets countered by a slow expensive one is a typical design. The cost curve helps check that the trade is fair: if the cheap unit is meant to win on efficiency, it should lose in a direct, expensive confrontation but win in cost terms when traded evenly. The build orders used in strategy games rely on such judgments, because players pick a path knowing what each unit costs.
Adjacent concepts matter. Sound deck building depends on the curve, since players choose their mix of cheap and expensive cards to match their resource supply. The archetype triangle often rests on curve differences too, where an aggressive deck uses the cheap end and a controlling deck the expensive end.
Why playtest data matters
Cost curves are models, and models are never perfect. A few points explain why designers treat them as starting positions.
- Players find combinations the designer did not model.
- The value of a stat changes with the environment. Health is worth more in a world full of weak attackers.
- Perceived value matters. A card that looks strong and is easy to use may be played more than a card that is slightly stronger but harder to use.
For this reason, curves are often revisited after release, and small shifts of one stat point or one cost are common. The numbers are tools for conversation within a design team, not laws, and good curves are those that leave several price points viable for players with different styles.