> More people with more money to spend means manufacturing volume goes up, so economies of scale go up, so the prices go down.
Back of the envelop, there are 260 million adults in the U.S., and 1600 GBP is $2000 a month for each of them. So, that's $6.2 trillion dollars a year that manufacturing efficiencies would have to make up for, in an economy with a GDP of about $23T. And that's assuming that mechanism would even solve the inflation problem, which is hurting my head to think about.
For the UK, it works out to about one trillion a year, off a GDP of three trillion, so an amount of money roughly a third of the entire economy would have to be made up for by ... companies getting better deals buying in bulk, and workers coming up with better processes than what they have now, and... uhh... other things of that nature? That sounds like wishful thinking to me.
I'm not against UBI, I just don't understand how this response actually addresses the most obvious problem with it. In fairness, I have not seen a better argument than the one you gave. Maybe there is another one.