Honestly, I can't understand people who think it's OK to split the bill equally -
When a menu comes it has the prices - I keep in mind the cost of each dish, the price of the drink, side dishes etc. Plus a tip - done.
I have a friend that organises trips and the chancers I've encountered! One guy tried to take over at the first dinner with his "we'll split the bill equally" - one lady had had two starters and wine, my organiser friend had one starter and water, etc - I pulled him up straight away (which he did not like, eye roll etc). The next meal I put down 35Euro, he took charge of the bill and kicked off when it was 6Euro short .. there were only 4 of us, each interrogated as to what they'd had (mine was 30Euro with 5Euro tip), on and on ... then he blurted out "oh, I've forgotten my dessert"!
Another one of my friends trips a few of us went to a very attractive restaurant (organiser went elsewhere) - when the bill came we each paid for our own dishes and I remarked they hadn't included the bottle of wine that I and one of the others had shared. Well, her eyes lit up, and I had to put her straight, I wasn't going to not pay for the wine! Goodness sake!