The people you described fit exactly the profiles in the book, “The Millionaire Next Door.”
I'll have to try to read that. Perhaps my public library will have it, so I can read for free. LOL.
But seriously, these people were just normal people who you wouldn't guess had that much money. They weren't misers, but they just didn't throw money around.
My son is in college, and I advised him to spend as he normally would for two weeks, but to keep a small notebook to record every cent he spent. That would give him an idea of where his money was going.
It's not the "big" items that destroy a savings plan for most people. The rent, the car note, the insurance payments... those are factored into their mental budget. It's the small things that can add up, and most people aren't even fully aware of how they can eat up the checkbook.
What kills a budget? Buying lunches rather than brown-bagging... in fact, just eating out period. That daily Starbucks. Taking the family to a Friday night movie, rather than a Saturday afternoon matinee. For young people, it is electronics... getting the newest phone the instant it hits the market. College textbooks bought at the bookstore rather than checking Amazon or another vendor.