Except that robot-based manufacturing only reduces the labour component of manufacturing costs - there's still the cost of the raw materials, of factory space,

Except that robot-based manufacturing only reduces the labour component of manufacturing costs - there's still the cost of the raw materials, of factory space, of buying the robots, etc. Some of those, such as the cost of the robots, actually go up in this scenario compared to less-automated manufacture. So the net result is that an increasingly large share of the price of products goes to mineral rights owners, land owners, intellectual property owners, etc and an increasingly small share goes to labour. Which means wages will plummet faster than prices.