How many copies has GTA: San Andreas sold?

How to get close to this number

Bracket it by the platform. This was the best-selling game on a console that sold on the order of 150 million units, and even the biggest title on a platform reaches only a fraction of its owners. A share in the high teens of percent of the install base gives a figure in the tens of millions, which is right.

The instinct is to anchor on modern blockbusters and guess far higher. But sales ceilings scale with install bases, and the market of that era was a fraction of today's — digital distribution did not exist, there was no long tail of discounted re-purchases, and a game sold for a few years rather than a decade. Records have to be read against the size of the market that produced them.

The technical point in the explanation is the lasting legacy. The map was too large to fit in the console's memory, so the developers built streaming systems to load the world continuously as the player moved through it. That constraint-driven solution became standard practice in every open-world game since, which is a bigger contribution than the sales figure.