And what is this constant deal with the salary of workers? I can't figure out why you keep bringing it up.
In order to make something you have to use either a spell or the craft skill. Skeletons obviously can't cast spells, and the limit of what they can do with the craft skill is earn 1 sp a day because they're untrained.
Interpreting it the other way gives you just as much nonsense, though. Mindless creatures can make DC 10 Knowledge checks and basically have perfect common sense. Even if you're cool with that, there's still the "Untrained workers make 1 sp a day" bit.
It doesn't provide common sense, but rather common knowledge, which IMHO is implied in the fact that they can obey 'simple instructions'. You can't obey a command such as 'close the door' unless you know what a door is and what the actions of opening and closing imply.
They don't close the door because they understand the concept of closing a door, but rather because you communicate the concept of what you want them to do. A nasty side-effect of being mindless is that you don't understand language.
Hell if I know, the uses of undead labor is mainly to eliminate the need for unskilled labor. So any task that requires no judgement or decision ability is saved. Transportation costs are greatly reduced, overland shipping times go down, etc. You could program one to clean the streets, quarry stone, etc etc, but when used to power manufactories, they're just the mechanism to reset a non-magical crafting trap.
This might actually be something. If you make a one-shot trap with a manual reset, it's a lot cheaper than anything with an automatic reset. While it might not be worthwhile with low-end traps, if you do it with something that casts Wall of Iron then you're saving significantly more money than it cost you to raise a 1 HD skeleton in the first place.
That said, such a trap is still expensive, and mindless undead are still incapable of producing the trap in the first place. As such, I still don't believe this rises to the level of "industrial revolution." Fact is, there are more than enough commoners to saturate your typical 3.5e economy doing this sort of thing, even if you need to get 3 of them to work in shifts instead of a single skeleton. This sort of stunt belongs more in the "Reducing costs of items" guide than anything else.