Costa and the other coffee chains are really internet cafes where you bring your own device to surf the net, their growth has risen at the same time as internet use. Coffee is just the mechanism that people use to pay for a chair and table and somewhere to plug in and browse. Before people would get a drink and maybe something to eat, consume it then leave straight away. Now people spend a lot longer sitting with just one drink, and that is why the price of the drinks has risen to ensure that they make a profit from consumers sitting there for much longer.