The tools of your trade, whatever your trade may be. I’m a housewife, myself, and I can’t tell you how glad I am that we spent the money to remodel the kitchen in our new-to-us house. I already had good pots, pans, knives, and gadgets (not that I spent huge money, but I spent a lot of time amassing the good stuff at good prices through the years,) and having a great stove, oven, dishwasher, even kitchen faucet makes my job easier, better, and even (in the long run) less expensive: I probably won’t ever need a new stove, for example - I found a 6-burner Viking gas cooktop on Craigslist for a real bargain. It’s heavy-duty, has very few moving parts to break, and suits me perfectly. My dishwasher is a high efficiency model, so I use less water per load. I found a great wall oven at a yard sale - my back thanks me every time I get a heavy casserole dish or roasting pan out of the oven. I use my Kitchenaid mixer about 4-6 times a week, and have for the past dozen years. It gets cheaper with every use, and I enjoy using it.
If I were a carpenter, or a mechanic, etc., I’d say the same: buy the best tools you can afford. They’ll last.
Not just cheese, but food in general: It doesn’t have to be the most expensive, but buy the best food you can afford. The freshest, the in-season, the least processed. If you’re gonna splurge, have real butter or the good chocolate.
Shoes. Always. And handbags or other sorts of totes/luggage. One good piece that lasts forever is vastly better for your budget (and the environment,) than 20 that last a year or two.
Not previously mentioned: desk chairs. Spending a few extra bucks on a really good one is better for your wallet, better for the environment (than replacing every couple of years) and better for your back (and wallet - what’s the co-pay for a doctor’s visit or chiropractic visit? How much vacation/sick time do you have to nurse a bum back before you start taking a hit in the paycheck? How much are you spending on pain relief if you have a back ache?)