I think it is human nature to gravitate towards people who look/behave most obviously like you, and to whom you feel a natural, comfortable affinity with firstly, and secondly to make tentative steps towards people you aspire to be like. (this doesn't have to be about financial/social status, but it often is.)
I am sure that the same would be true in reverse as well; if one school gate mum appeared to be a 'posh,' well spoken, slightly serious professional in an expensive car and a sharp suit then she is probably not going to be inundated with invitations for coffee from the core group of SAHMs from the council estate. The difference is, she probably doesn't notice or care, because she is not looking for signs of validation from them in the first place.
I always made friendly conversation with all the mums of my DCs friends, even if I knew deep down they were not really the type I would usually be good friends with. In one place I lived I was definitely one of the most high income mums at school, and several of my DC's friends were definitely among the lowest. I got on great with their mums; some of them I became very fond of and we would spend ages gassing and having coffee if I had to go there to pick up a DC, or if they came to mine. But I was aware that there were differences in our lifestyles that made it unlikely that we would be good friends much beyond that. Would I have invited them for dinner? No. It's nothing personal - it's just the way things are. And frankly, they would probably have been horrified if I had.
If you don't live in a total bubble of either privilege or disadvantage then you will need to mix with people from all backgrounds, especially if your DCs are at state school. So if people came to my house and always said 'Oooh, it's so big!' or 'Oooh your DH does that for a living?!' or 'Oooh you are so much posher than me' or 'Ooh, how do you manage to have such a fabulous holiday when I can't afford a caravan in Clacton?' then it becomes a bit awkward after a while to just have normal, relaxed conversation without the wild difference in our incomes always being the elephant in the room. I got scared to say anything about my life for fear of making other people feel bad about theirs, and relaxed friendships can rarely work like that.
People often perceive it as a rejection of them based purely on their status but in reality it's much more complicated than that.
I don't think I would ever seek to attract or reject a potential friend based purely on how much money they had, or how beautiful they were though. I have known people like that and they are arseholes.