You can tell from the doorway which bed is dressed in something good and which one just looks expensive in a photo. The real thing has a kind of weight and drape to it, the sheets settle into soft folds instead of sitting stiff and shiny, and the whole bed looks slept in even when it's perfectly made. The cheap version looks fine for about a day, then it pills, it shifts around at 2am, and it has that slightly plasticky sheen under lamp light that no amount of fluffing fixes.
This is the stuff for the primary bedroom you actually spend time in, not the guest room that gets used twice a year, and it makes the most sense in a house where you're willing to launder and iron or at least don't mind sending it out, because good cotton and linen want a little care. It's lovely in winter when you want weight without bulk, and just as good in summer if you pick the right fiber, since a breathable percale or linen sleeps cooler than most people expect. Where it falls short is anywhere high traffic or high mess, a kid's room, a shared bed with a dog who thinks he's a lap dog, a rental where you're moving in two years and don't want to baby anything. In those rooms, buy something sturdy and ordinary and save the good stuff for where it'll be appreciated. Color wise, go quieter than you think you want. White, ivory, a soft oatmeal or clay, a deep but not dark navy, these all hide wear and wash well for years, while bold prints and pure black show fading and pilling first and fastest. The difference between a well made set and a disappointing one usually comes down to things you can't see from across the room: long staple cotton instead of short, a tight sateen or percale weave rather than a loose one, real mother of pearl or coconut buttons on the duvet cover instead of plastic ones that crack in the dryer, French seams that lie flat instead of puckering after the first wash, and a hem that's actually sewn straight. Pick it up before you buy it if you can. It should feel heavier in your hand than you expect, and when you crumple a corner, it should spring back instead of staying wrinkled.
Good bedding doesn't announce itself, it just makes the whole room feel calmer, and that's worth more than almost anything else you'll buy for the house.