What benefit would someone have to not pass on cost savings to consumers if they had a super effective robot to do something? And regardless of their motives, how would they stop it from happening? Patents have limited lifetimes and and techniques developed will be quickly replicated/democratized.
Perhaps someone could corner the market for a while, but not indefinitely.
In the end, the result of automated production will be downward pressure on prices, with consumables trending towards $0.
With this in mind, it strikes me that the pessimistic predictions stem from the idea that there is a secret cabal of the "wealthy" who take great pleasure* in keeping their fellowman down. Today, by many measurements people living in wealthy countries have a standard of living so far superior to that of kings of old. Has the secret cabal been just lying in wait until now to strike?
* sure, some percentage of billionaires are probably sociopaths, but I'm sure most are not.