Yes, companies can sometimes produce technologies at lower cost. But my thinking is that when the technology is as much of a security threat as AGI, governments would use their power to prohibit private development of it (just as governments prevent private selling of advanced military weapons). Combined with the fact that governments are not totally ineffective, this makes it plausible that the first AGI will be built by a government. Of course, governments might not be first, especially if private companies are fast enough to outrun government prohibitions.