If the robots are cheaper than human labor, there will be more goods available and the goods should be cheaper.
The problem will be that we are used to matching supply and demand by rewarding productivity, not real shortages.
Ironically, the very best jobs in extremely productive economies like the US are detached from productivity and linked to perception and politics and the like (or do people believe that every $10 million CEO is that much better than the next guy on the list).
> robots is that you can also stop production instantly if demand goes down. You have much fewer costs when not at full capacity.
I think you have this exactly backwards.
In a highly automated factory the main cost is capital, i.e. the machines might cost decades worth of payroll. So having them sit idle is extremely expensive, or to say it another way, producing nothing saves you almost no money.
A low-automation factory is the opposite. Big traditional garment factories are basically just sheds with some tables. Almost all the cost is workers, and in many places & times you only hire them when you get a big order.
The automated garment-sewing machines (if we get there) can't do anything else. Factory robots aren't very C-3PO. Whereas the sweatshop workers can be assembling cellphones (or building rice terraces) next week.
> there will be more goods available and the goods should be cheaper.
Did we ever stop and consider that increasing production/consumption might not be beneficial ? I have a hard time imagining that all that matter is consuming more things and cheaper things.
This is bad news for most of the Southern Hemisphere with young populations which will continue to grow till the end of this century.
Unless something changes economically or in pop growth, there are going to be massive economic problems.