Usually do rounds or split bills if out with larger groups/friends on similar incomes
With friends who have a lot less money I will try and spend more on them, send treats etc.
If it's a full weekend away with hotels, meals, drinks, activities then we use Splitwise app or one person pays for everything and we all bank transfer at the end.
There is a lot of buying each other theatre tickets, meals, spa days etc. for birthdays so spends are covered in advance
I have lent money to trusted friends, the most was £15k short term interest free to bridge a house move.
Also given money, bought shopping etc.
So far, I can't think of many friends who have taken the mickey or taken it for granted - I do feel very lucky with the friendships I have
Just one, who I rent a house to, and she fell way behind on rent whilst still posting about holidays & days/evenings out. That hurt, but she's back on track now thank goodness
Mostly we all have the same thought that the odd drink here and there over 20/30 years we've been going out will all equal out eventually
Life's to short to be socialising with a calculator for me - but I maybe get it if you have flakey mates!