Do cheap dupe perfumes from luxury brands actually work?

I've tried some luxury fragrance dupes and it's weird because at first they smell almost identical, but the staying power is definitely shorter compared to the originals - after a couple of hours it fades away, while the real ones last pretty much all day. It also depends on how much you're willing to spend on the dupe, because the cheapest ones are just a letdown, but the pricier ones work pretty well if you're not too picky about longevity.