The detail that supports the idea that social class impacts people's sense of reality is:
"... [There was a bill that he would pay with a real two shilling piece, and it was real, all real, he assured himself, fingering the coin in his pocket, real to everyone except to him and to her ...."
This statement illustrates how the characters grapple with their perception of value and reality surrounding social experiences, suggesting that their social class influences their understanding of what is "real."