Isn't (2) a relative issue? In other words, if everyone else also worked three hours a day instead of eight, then the prices of goods would change to reflect that.
There would be only 3/8 as much "stuff" (including services etc), modulo productivity effects, to divide among the same number of people. So on average, you'd be able to afford 3/8 of what you could in a 8-hour-a-day world. Regardless of whether prices changed and in which direction.
What is consumed, must have been produced. If less is produced, less is available to consume.
Wherever possible, a company would have three workers filling out a shift rather than one.
I think there would be productivity effects, though, as noted by another poster. And not everything scales linearly in the necessary manner for this to work (but many things do). One upside, though, is that the number of jobs would drastically increase.
There would be only 3/8 as much "stuff" (including services etc), modulo productivity effects, to divide among the same number of people. So on average, you'd be able to afford 3/8 of what you could in a 8-hour-a-day world. Regardless of whether prices changed and in which direction.
What is consumed, must have been produced. If less is produced, less is available to consume.