Take it you've not owned a Duke? They're several magnitudes worse
I have owned Aprillia which have a similar reputation but prooved to be, well obviously not cheap, lets say, not unreasonable.
That piece of kit for the duc is the handguard, mirror and indicator assembly and is obviously designer kit. Take a bike like the XT1200 Super Tenere, Yamaha's closest equivelent, and those parts are going to cost you well over a ton a side. The best prices I can find for the duc show their kit costs over twice as much, but lets be honest here, which one looks sexy? And which looks like it belongs on a tractor.