edit: it depends really too what we mean by wealth. If we define wealth as being employed, good lord wealth is zero sum. The amount of jobs the modern tech sector has created has been pitiful, with poorer compensation than many unskilled fields. If it means by possessing things, its a mixed blessing.Plenty of free or low cost content, though large staple goods like houses or cars are climbing up there.
Also, Martin Ford mentions something called the lights in the tunnel problem. Imagine a tunnel full of lights that represent the wealth of people. In the modern world, a handful of lights shine intensely bright, while increasingly more are dark, dim, or low-intensity. But the tunnel is dark, because a handful of lights can't generate enough light to make it illuminated. He used it in context of automation, but this is modern wealth creation, and eventually it will reach the point where the ones controlling the wealth have done so by dimming so many people that the tunnel goes dark.
Take into account the increase in wealth of all the customers (as they get more for their money).
There’s the matter of supply and demand. Nothing comes out of nowhere. When you create a thing, you demand some resources, and then the next person has to pay more for the same resource. Even for a creative output from yourself, you need food and shelter. (And what a controversy shelter has become, in the San Francisco Bay Area.) In the ideal case, the resources you consume enable you to create more wealth than you cost to the rest of society, and thus society benefits. (Not the now homeless person in San Francisco, though.)
Technology is sort of weird in that consumption actually decreases costs, in some situations. The semiconductor companies are paying exponentially increasing costs for state of the art fabs, and they need to keep the fabs selling at peak capacity to make a profit. Also, software is merely knowledge, with very low reproduction costs, so a small production of software can be consumed on a vast scale across the planet, and facilitate the production of more software, enriching people’s lives. This does not make it easy to reward the creators fairly.
It is sometimes. The profits "earned" by Wall Street are nearly always zero sum, for instance. They are not making other people richer.