Rustle has it spot on (not for the first time)
The restaurant meal analogy does not work - if I am invited to a meal in a restsaurant with friends I get exactly the same benefit as they do - meal, company etc, and I naturally expect to pay my share. When I go flying I go for my benefit - if someone wants to come with me for company that's more benefit to me. If they enjoy it then we're both happy.
IMHO if you need your friends to subsidise your flying habit you need to look for another hobby, or you are likely to end up with no friends - sad but true.