Since the standard of living for the 'society of producers' has risen by a good measure since the time 'someone' said that, I guess 'someone' has been proven wrong by a good measure.
Then it says "the means of production are not mere means for a constant expansion of the living process of the society of producers". A repetition of what was said before. The means of production is not JUST about improving the standard of living for the society of producers. It is about other things. You're claiming it says somewhere in there that the standard of living will not rise for producers. It does not say that. You have not contradicted anything.
We live in a day and age of shareholders rights and profit and dividend being the key objective of corporations. This is actually codified into law. Layoffs, mergers and salary freezes/cuts are seen as good things. This is not a secret at all, just read Business Week or the Wall Street Journal. So the original point holds. "The means of production are not MERE means for a constant expansion of the living process of the society of producers." You seem to be ignoring the word mere in that sentence, and the sentence before it.
[1] Since 'not mere' does not exclude anything the means of production could be means for everything. But technically your point about the non-implication is correct.