Anecdotally... I have a close friend who is a PhD, has tens of thousands in the bank, a great job, and absolutely loves the dollar store.
It's amazing.
Which is only annoying because similar stores in Japan (which for me are a highlight of any trip to Japan) only charge ¥100.
I don't know if it's because of proximity to China or because Daiso knows they're offering better stuff than their literally $1 competitors here in the U.S.
"You get rich by saving what you have" is a nice feel-good story, but you get a lot richer by getting magnitudes more in income.
You can be frugal enough to live a comfortable middle class lifestyle -- but the people who are rich just make a ton more than you. That's it, that's the secret!