Unless you've had something very similar and the price difference is pennies.
I went out with a group of friends the other week, I don't drink alcohol and most of them do. I had a starter as a main course, and two diet cokes.
It came to £33 each when splitting, even though my starter was i think £8.99 and two cokes around £8 in total.
That included a tip, but that would've meant me leaving a £16 tip which sounds extreme. I wish I'd spoken up really, next time I will but you're labelled as 'tight' if you do that. I asked them to confirm again, and nobody said 'you've only had a starter/soft drinks whereas we had more.'
It does put me off going sometimes but I suppose if your friends call you tight/cheapskate then they aren't real friends? I'm on more of a budget too.