In other words, if making things more durable results in people working fewer hours, then we need to know whether that results in negative income repercussions for workers.
A rudimentary example:
1x disposable widget took .5hrs to mfg. market price =$10 and lasts 1yr. CO = $10/yr
1x durable widget takes .6 hrs to mfg. market price =$50 and lasts 10 yrs. CO = $5/yr
And you extrapolate that...
So, yes, your costs go down over time, but so do your wages, so the deflation has to be measured so that earnings don't go down quicker than cost of living/cost of goods and services. Commensurate.