I track my expenses with an app called toshl. I love it, it has all this small monsters as graphics and stuff. However, I have a tag for "friends" so I track how much I spend 'on' friends. It is kind of a normal expense like coffee and coffee makes me happy.
The other day I came into the office and couple friends were already there. I wanted to get a cappuccino - the best in town - and asked if they wanted one too adn yes they did. To get back from the coffee shop has quite a challenge with 5 cappuccinos - made me really happy to see them smile, cause if someone brings me a cappuccino I am really happy as well!