SC Project owner here and I totally agree with everything you said. Well, almost everything, I think you're kind of exaggerating on the price part. But everything else you said are simply objective facts and I don't see anyone trying to argue with you.
Any exhaust is designed as a compromisation of different things (looks, sound, performance, weigh, emissions, cost, etc). I don't think the SC is made poorly, it's just a solution that is looks & sound oriented. So, if you're mainly interested in those two things when looking for an exhaust, it's one of the best solutions out there. It really is not designed for performance, but not because the company lacks the know-how (they're in MotoGP after all) or because they tried to make a cheap product(the quality of the product is top notch). They simply went another direction than the manufacturers you mentioned.
By the way, I'm pretty sure nobody's spending 500-1000$ to gain those 1-3hp. If you're really looking for performance, an exhaust is probably one of the worst power per buck mods you can get. So just pick the exhaust you like best and enjoy it the way you want to.
Agreeing! (SC-Project owner here!)