There isn’t actually a coffee posted on the menu for 3.50 unless you asked for a large and alternative milk?? That may explain why you were charged 3.50 as they add 50p to your coffee if you ask for a different milk and 30p to upgrade to a large. They do to mine anyway which I can understand.
Makes sense as most of the standard espresso coffees are priced between 2.50-2.70?
Who knows, they could have reduced there prices. I do agree it’s on the pricey side but you get what you pay for
Took a pic of the menu for ya