I've not read every post, so forgive me if someone else has already posted the Miss Marple quote about the way poor/rich people dress.
Its in The Body in the Library, and she's asking about the choice of dress Ruby (common as muck but pretty and won the heart of elderly wealthy man, ends up dead) wore to go for a night drive.
It was saying that people of Ruby's class would always wear their best clothes for an occasion, even if they weren't the most suitable for what they were doing. That a girl of Miss Marple's class would have changed into a pullover and wool skirt for a night drive, but if a girl like Ruby was going to change, it would have been into her best dress.
And I think that's the bit that makes many designer bags look fake or fail to make you look rich when carrying it.
IME, "older money" types might own a LV Neverfull (the bag discussed on that thread), but they'd have bought it because they wanted a good quality canvas bag to use as a beach bag or for as a casual shopping tote. The women I know who grew up wealthy would always carry a bag that went with their outfit/was appropriate for what they were doing, not just always take their most expensive/best bag. They wouldn't take that casual bag to the office, if a £50 one was more appropriate, they'd take that.
(I am still rubbish at this, im definitely more Ruby than Miss Marple)