If the AGI is open source and operates through a decentralized platform, that everyone/no-one owns it, and the upside will be fully distributed to end users.
But even if it stays in private hands, one company monopolizing a technology and keeping it expensive/out-of-reach is generally not how technological innovation works. There is generally intense competition between providers, with each aggressively cutting prices to capture market share.
But even if it stays in private hands, one company monopolizing a technology and keeping it expensive/out-of-reach is generally not how technological innovation works. There is generally intense competition between providers, with each aggressively cutting prices to capture market share.