I think it is pointless and sort of silly to even think of fragrances houses in these terms. Seems to be a very popular thing to do here on Basenotes, however.
Even after all this time, there is still dispute/confusion as to what is "niche" and "designer". Then, with PrivĂ© / Exclusif / whatever lines that traditional "designers" come out with - only blurs the lines more.
I personally don't think it matters if the company also manufactures shirts or not - it doesn't affect the fragrance at all.
Seems many posts here really mean "16 year old kid can't go to mall and get this, so I will safely be "unique"" when saying "niche"
Maybe breaking down by "cheap" / "expensive" would more clearly express the intent of the delineation.