Well, Scully's suits were all tailored, and cosplayers are probably putting together her outfits from retail stores. It's amazing how hard it can be to find an over-the-knee pencil skirt from an affordable source when it's not en vogue (and I consider "expensive" to start at Urban Outfitters).

For example, no matter what the season, if I walk into Forever 21 looking for a dress, and find one that fits perfectly, it will always be too short and almost always have a neck that plunges way too far.