I have mentioned my future mother-in-law’s frugal ways on here before.
She reuses teabags. Keeps them piled on a plate in the kitchen, and uses them over and over again. Fair enough, she likes weak tea, but she makes tea for visitors out of second hand teabags regardless of how they like their tea.
She buys foods that her family don’t really like, because they last longer. So, she’ll buy a breakfast cereal the kids hate, and then the kids will only eat it when they’re starving. Extend this to everything in the house.
My parents spent my entire childhood telling me off for reading in the semi-dark (“You’ll ruin your eyes!”). My fMIL has turned the light off on me to save money and electricity. Even when it’s too dark to see the book properly, she didn’t approve of me having the light on to read if I was in a room by myself.
She kept buying lawn edgers from garage sales because they were cheap. The fact that they were broken didn’t deter her - she bought a heap of the same type, and tried to get her son to raid them all for the parts to make one that worked. Unfortunately, all of them had exactly the same fault. So she keeps them in the shed in the hopes that one day, she will find a one that will have the part she needs to fix one of the other 6 she already has.
When we bought our house, the garden beds in front had bark - which I like - and the ones in back had those little red stones (Scorria?), which I hate. We were talking about the gardens and I said I wanted to get rid of the scorria because I hate it, and she got very angry and insistant that we don’t get rid of it because it’s expensive to buy. Now, to me, scorria is worthless because I dislike it but to her, because it costs so much to buy, liking it or disliking it is irrelevant and she thinks I should keep it. It’s this thinking that leaves me totally confused.
My uncle used to have two televisions - one on top of the other. Both were ancient, and while the picture tube was gone in one, the speaker was gone in the other. So to watch TV, they’d turn both on, the top one provided the sound and the bottom one the picture. They were too cheap to go out and buy a new TV, and used this arrangement for years.