Well spotted, I missed that 
Tom made it clear in the annual report that this isn’t where the bulk of Monzo’s costs are coming from -
It costs a fraction of a per cent to process each transaction, but it adds up when you’re dealing in billions.
so some of the details in this story might be a little off..
I’d be surprised if Monzo expands to the US before Europe, even though Tom’s obviously very keen to get started there because of the challenges of setting up shop somewhere so far away & their relatively archaic payments systems. There’s more detail on Monzo’s plans for US expansion here -