It doesn't have to be super drastic - When I graduated college and got a decent job, most of my social group was making less than a full time minimum wage salary, bouncing around couches, or staying with parents - with no hope of it improving. I felt the resentment a lot, even though it was subtle, and constantly felt obligated to pick up checks if we did anything I wanted to do, because what I could afford to spend on an outing was significantly different. Then that builds resentment over time, etc. People don't like seeing people with more "stuff" than they have at a really deep level. Looking back I am not sure that I could have done much to salvage it, the only friends that survived out of that era were the ones that were able to bring themselves out of their situation as well.