All these stories are familiar to me as well.
Everyone ordering the most expensive food in the hope that it will get split evenly and their meal is subsidised, or that someone (I often did it) would just say at the end "this is on me".
Then there's those who have worked out that if they pay last they can ask "How much collected so far?" so they make up the small difference, because everyone else has dropped in a little extra for a tip.
I've ended up telling people "No, your meal was x amount - the extra in here is for the staff, not to pay your meal". It's a bit embarrassing but it happens EVERY time.
Splash