Why was Ponyboy so surprised that he got along with Cherry in The Outsiders?

Ponyboy was surprised that he was friends with Cherry because she was part of the Socs', the rich kids who had everything.  How could she possibly have anything in common with Pony when he was from the other side of the tracks.  He was a Greaser and she was a Soc, total opposites.  Pony thought of the Socs' as spoiled rich kidss with no consideration for people's feelings or any else that should have mattered.  Ponyboy is so sensitive and caring, that he doesn't believe a Soc would understand him.  He groups Cherry as just another Soc that would usually be cruel to him and treat him badly, just because of his background and social status.  The Socs' looked down upon the Greasers.  They thought they were better, just because they had more money.  Socs' didn't associate with the Greasers because to them, Greasers were poor and pathetic, low class compared to them.  So Pony figured, Cherry would be that same way, materialistic, unfeeling and shallow.  That was not the case, however, and Pony soon found out that he and Cherry had a lot in common.  She wasn't like the other Socs'.  Cherry Valance was warm, intelligent, caring and thoughtful, to his surprise.  The two became friends, regardless of their obvious differences.