How do you decide where quality matters? Is it just a matter of personal preference or perhaps there are certain things that everyone values quality in?
Here is an example of me trying to make a decision concerning cost- I was trying to decide which brand of blue corn chips to buy today- both had the same nutritional profile but one was a dollar more expensive. However, I've gotten the less expensive brand before and found that the bag rips easily because the material is so thin, so I decided that perhaps it's better to pay an extra dollar to get the brand that has a rip-free bag. This is the kind of thing I'm talking about.
I frigging really don't know how to make decisions like this as I'm just not practical. It's hard to know what's important. It becomes even more relevant, of course, when you need to buy more expensive items like a car or an appliance.
That's the thing, there isn't an absolute answer. It depends on your personal priorities. So for me for example, I want to be saving some money for a house eventually, some money for retirement, and some money to earmark for paying off my student loans when I graduate. My income's retardedly low now so it's mostly to get into the habit of saving (aiming for 30% net to those 3, if I can). It's the first time I've had a steady income so I'm not in the habit of actively saving for goals; before, I just had one savings fund.
So for me meeting that goal is important enough to not splurge on things, but I still want to enjoy life and I might cut the savings down if it gets ridiculous, since it's not that important right now (given my low income).
That line for what's a "splurge" vs. something that matters to you, well that depends on how important things are to you. In your example, if I don't really mind dealing with the rips, or I think I can be more careful with the bag and it won't rip, I would get the cheaper one. If it really upsets me and ruins my day when I have to clean up chips from all over the floor, I'd get the more expensive one. (Or if I wanted to be more green and go with less plastic used, maybe I'd go with the cheap one

)
I buy almost everything generic the first time I buy them (unless I've heard the generic is bad for that, or know that similar generics are gross), and keep buying it if I like it. Some things the generic is really awful, sometimes it's a bit worse or about the same, and sometimes it's even better! (Mostly just the PC brand, it seems a lot better than the other generics). Usually if it's reasonably close in quality to the brand name I'll stick with it - though if you watch the sales brand names are often cheaper since they usually go on sale for cheaper than the generics which rarely go on sale.
----------
Food is where I spend most money. I like delicious things. I buy things like goat cheese and brie sometimes, and I'll buy a tub or two of haagen daaz when it goes on sale for 3-4 dollars (fairly regularly but not all that often). I buy fresh sourdough bread or rye bread every so often even though it's way more expensive than that gross processed white bread (which I no longer buy, but eat occasionally for grilled cheese only). I buy a lot of fruit and berries and things like asparagus and avocados which aren't necessarily the cheapest things to eat. I buy triscuits when they're 2$ because I love them. I buy those big blocks of chedder cheese and eat more than I should. I buy tsatziki dip when the pitas are very fresh because I can't make that stuff taste like the stuff in the stores and it's so good. I buy a lot of milk and chocolate milk sometimes if it's on sale. I usually buy all these things (except milk) only on sale, but I could be buying cheaper things. I'll also spend more than I need to in an attempt to have a somewhat healthy diet.
But some people could be happy spending way less on food, and others wouldn't be happy without spending a lot more, I'm sure. You just have to pay attention to what makes you really happy, and what you're just eating (or doing) out of routine or because it's there.
Bottom line: I want to get the best value for my money, which often means buying cheaper things, and fewer of them.
I've noticed what seems to be a particular dislike of cheap stuff on the part of ISTPs.
Yeah...it's not that I mind "cheap" stuff, I have a lot of it, but mostly it's been free or mostly free stuff that's useful to me. I don't mind spending a few bucks at the thrift store for mediocre pots or something, but I wouldn't buy the cheapest new set at Sears, for ex. If I'm putting a reasonable amount of money towards something, I want to get the best value for it, which usually means paying more for higher quality that will last, and/or paying more for a superior experience (maybe better heat conductance in the pot, or something).It's probably not going to be the most expensive one either but I'll probably do some research on it first rather than just getting some cheap one.
Well, I think there is a difference between pursuing one's passions in the more minor/artful ways of life and being another Richie-Rich businessman. The more artful way may not be frugal in respect to the hobbies, but it demands less spending in general if it doesn't generate as much income as the more ambitious route would. Ambition is often thought to accompany luxury.
It's true that a lower income suggests frugality, but there are way too many people with senseless consumer debt to make me believe that frugality comes naturally with a lower income. Some rich and even very rich people are quite frugal, too. Probably not to the point of eating rice and beans every day, but frugal compared to the "average" person.