If the quality of the replica is very good, I really don't see what the issue is.
Wings West made a very nice knock off on a discontinued TRD elegante lip kit for the Celica -- it looked great, was high quality with excellent fitment -- also cost considerably less than the (again DISCONINUED, thus nearly impossible to find) TRD original.
On the other hand, I had an original greddy lip and that was a POS made out of plastic -- I would have happily taken a knock off if it was less expensive and superior quality
The Amuse kit may be top notch, so perhaps a knock off won't do it justice.. that said, these aren't "exclusive", just pricey.
Much of the cost of a kit that isn't simply mark-up, BTW, is the cost of the molds, not R&D. A really good company will not reuse the mold more than a few times to ensure each piece comes out perfectly.
That's fine, so long as the fitment is always perfect -- even the big names cut corners sometimes, and you wind up paying for the name only.
Also, part of what you are paying for is the import fee, not the quality or to compensate the manufacturer for his alledged R&D (was this tested on a track or wind tunnel or is just cosmetic??)... it's your money.
Of course, there are probably some sort of copyright issues, so I suppose you could make a legitimate case against knock-offs on the basis of that...
I'd love to hear what folks around here think of Rota wheels, which are well liked by autoxers and road course racers, but often dismissed as "cheap knock offs" by others.
Just a thought... are people concerned about "high quality" or being able to say "it's an original"? Fair enough on the former; on the latter... again, it's your money...