Simply put, chips change in value in tournaments because of the prize structure and the fact that most players leave with nothing.
For example if 10 people buy in to a tournament for $1000 and each gets a stack of 1000 then there are 10000 chips in play and $10000 in the prize pool (assuming no rake for simplicity) so each chip is worth $1. But no-one can cash out and there must be one winner. So if the pay out was 1st: 50%, 2nd: 30% and 3rd: 20%, at the end of the tournament one player will have all the chips (10k) but win 5k, making each chip worth 50c.
The actual value of chips changes throughout the tournament and becomes more important as as the game goes on.
As stated above, look into ICM, tournament
equity and $EV vs chipEV.