My friend almost always picks up for me and doesn't charge me anything, but I always roll a couple and smoke him out afterwards. Of course, I'm also the type of friend who will show up with gifts for no damn reason. He always jokes that I've bought him all his good glass pipes, which is almost true. I think with real close friends, there is so much give and take you shouldn't get too uptight over it. If they are just acquaintances then they should kick you a juicy bud at the very least.