Endogenous Value

‘Endogenous Value’ is term used to describe when something in the game is given an actual value to the player.

This value can be either 
Economic, this mirrors the material wealth of the world, having 'money' to purchase new goods, eg. new weapons in 'Ratchet and Clank'.

Emotional, this is where an object is valued more because you have won it through a test or quest. but can be where you put in extra effort to undertake a loyalty mission for a squad mate in 'Mass Effect 2' which allows them to survive longer in the game.

Forced - this is extra value attributed just for playing the game. Things that are hard to achieve generally have more value than those which are easy to achieve eg. a sword that has been won through defeating an enemy or completing a number of tasks has more value than just a single task, eg obtaining Mithral objects in 'Lego Lord of the Rings'.

When designing a game the questions you need to ask are "What is valuable to the player in my game? How can I make it more valuable to them? What is the relationship between value in the game and the player's motivation?"(Williams, A. 2015)

Bibliography
Williams, A. (2015). The Importance of Rules in Sports | LIVESTRONG.COM. [online] LIVESTRONG.COM. Available at: http://www.livestrong.com/article/485675-the-importance-of-rules-in-sports/ [Accessed 26 Apr. 2016].