Go to any place that sells games. After some amount of time the price drops.
Back when GTAVC first game out it was $40-50US, now you can get it for $20US.
Another great example; Battlefield 1942 originally $40-50US then add in the 2 expansion packs at about $20-30US each totally $40-60 (2 packs) grand total $80-110US, now Battlefield 1942 World War II Anthonlogy (BF1942 + 2 expansion packs) for $20US at
Bestbuy. And yes people still play BF1942, just not so much the expansion packs, mostly the original or mods (usually DesertCombat), even though BF2 is out.
Battlfield Vietnam's price is also down from $40US to $20US.