well thats the thing. u can only put a certain amount of objects on the screen because of the space allocated in your disc. i am a halo custom edition modder and i have learned you can only go up to a certain amount before its time up. the "budget" just represents how many mb/gb are free on the disc and the "cost" is actually the megabite usage by the object. a standard metal wall on halo CE is 1 mb
Say we have all the original elite armour from reach, and 3. but you implement the arbiter's armour after getting a certain achievement like 'complete the game on legendary without dying more than 8 times in a row'