You're right - we can get closer and closer to an absolute measure by looking at many brains and AI's solving a problem, and converging to maximum performance g

You're right - we can get closer and closer to an absolute measure by looking at many brains and AI's solving a problem, and converging to maximum performance given a certain amount of hardware by tweaking the algorithm or approach used. But I think proving that maximum performance is really the ultimate level, from first principles, is a much harder task than looking at a performance graph and guesstimating the asymptote.