Now that steampunk is fashionable, it will be less fashioned. Now that it is an industry, it will be less industrial. Now that steampunk is a type of decoration, it will of necessity have more (and so less) decorum.
Steampunk is the one subculture that can remain independent while going mainstream. It can do so because it recognizes implicitly that the clothes really do make the man (or woman). What you see really is what you get? Gears on the outside, that's because it is gear-driven. Steam steaming forth, that's because it is steam-powered.
This eye-piece? No, I can see just fine, but since I squint to wear it it corrects for the squint.
For steampunk, style is substance and substance is style. There is no getting underneath the exterior, because the visible is what lies beneath.
This alternative history you think you are fashioning. No, it's not alternative. It's the history you have just departed, more real than you are.
Steampunk does what science fiction only dreams of--it makes real the real world. It fictionalizes the fiction. It steams dreams and punks punks.
All of which is to say, if Prada wants to sell high-end fashion of a certain steampunk variety, derivative and original at the same time, this is all to the good, because steampunk really was never very good at not being fashionable.
Steampunk really was always about fashioning.
Makers gonna make, and Victorians march to victory.
And that steampunk couture, all that style and those looks and those pictures you take of yourself to hand out to others? All of that really is the deep down most abidingest thing.