- The wonderful, amazing, rare ingredients. Some perfumes contain rare flower petals or the essence of a rare root (think tuberose and jasmine, both quite pricey). Others have synthetic ingredients that are hard (or at least expensive) to make.
- The marketing. Some companies spend millions to market a perfume that's hard to sell. You are the one paying for that marketing in the end.
Unfortunately, it's hard to figure out if you're paying for the marketing or the rare materials. Ingredients that are easier to come by or most synthetic fragrances cost a lot less.