Economies of Scale
The value of new elements is greater if you already have some of the same type. (Alternately, the cost of each new element decreases marginally the more elements you have).
For example, in a fantasy-strategy game, if your magician units draw strength from each other, then the value of a new magician is greater if you already have many others. (Rollings and Morris 2000). In Monopoly, there is an economy of scale in having two properties from the same group color (Boardwalk and Park Place, or Connecticut, Vermont and Oriental Avenues) because the owner can charge double rent for unimproved properties in that group.
The opposite of an economy of scale is a diseconomy of scale. This occurs when the marginal cost of each new element increases the more elements you have. This would be the case if, for example, the magicians became weaker the more you had available or if you had to charge half-rent for unimproved properties in a group.
In Monopoly, there is an economy of scale in having two properties from the same group color (Boardwalk and Park Place, or Connecticut, Vermont and Oriental Avenues) because the owner can charge double rent for unimproved properties in that group.
One must gain as much technology, land, and power as you are able, to achieve a definite advantage over other players. There are advantages in population, income, and trade by controlling more of the map.
Star Craft is a an example of an economy of scale. As you gather more resources, you are able to build more resource gathers thus increasing your rate of resource gathering. Also when you have enough resources you are even able to expand to one of the other resource nodes spread around the map in order to speed up resource gathering even faster.
Command and Conquer
Red Alert 2 the prism towers rely on each other to channel an attack. For each prism tower there is the attack power is 2x stronger than before.
Super Mario Bros. 3
In SMB3 for the NES, there is a mini-game at the end of each level in which the player is awarded a mushroom, flower, or star. Once the player collects 3 of these awards, the player is awarded a life bonus. The quantity of the life bonus varies depending on the whether the awards match or not. Getting 3 stars is the best award, followed by 3 flowers, then 3 mushrooms, and a non-matching combination being the weakest. This is a weak example because it does not play an integral part in the game.
In Diablo II: Lord of Destruction for the PC, set items are an economy of scale. Set items provide additional bonuses when items of similar set are equipped. As a result, there is higher demand and value among traders for more complete item sets.
Rollings, A. and D. Morris (2000). Game Architecture and Design. Scottsdale, Arizona, Coriolis.