As soon as those computers are cheaper than human labor, of course it makes sense. I wonder what our idea of low skilled jobs will be in the coming future.
If it cost even $100K for a computer cashier you would come out ahead within 2 years, and you'd still have 3 years to deduct the remaining $60K in CapEx assuming a 5 year deprecation period. Why on earth wouldn't you do this?
This is why we need to start thinking about how to handle the loss of these low-skill jobs now. It's going to happen, and it's not going to be pretty if we don't plan for it.
The US is pretty much ZPG, if you discount immigrants. So, one way to address the issue, is to be more selective on who you let into the country.
Europe and East Asia (but not SEAsia) are also naturally decreasing in population. So, there may be a natural effect which may counteract the contraction in jobs in highly industrialized/mature economies.
Places which have not addressed their pop growth may be in trouble; however, if we look at China, they proved pop growth is manageable.