You seem to be quite the expert on what is a scam and rip off for costs. I'm guessing you must have hands on experience in custom fabrication and welding and have engineered product from the ground up and done so in a manner to recover your costs and keep your guys working and keep the lights on. Do tell. Curious to know about your background.
If you're wondering why all the responses on beware of Chinese sourced parts, I'd say it's because we've watched quite a few roll through here over the years with their "just as good" mag rides, or stereo head units, or whatever, and well, yeah, they've worked out so well for many that they get trashed, and the person was back to ground zero and starting over, but sure, some have been happy.
And sound of the exhaust is a taste thing, and some have posted back after a period that the cheap exhaust had annoying resonance or just tiresome qualities to it so that even though it seemed good at first, they were trashing it a year later.
If you decide you want something that's a good balance of price and engineering from a well established company with a good reputation, here's a Topgear system that may fit the bill. I'm not 100% it's the right one for your car. Honestly too busy to put too much effort into this, especially since you don't really want to hear what people with experience have to say, even though your post starts off asking the question:
Audi R8 V10 (With OPF/GPF) Valved Catback Performance Exhaust 2020+ Euro Spec
www.topgear.co.uk
And as mentioned early on, Avior builds some nice systems. They can be a bit backed up and slow to respond, but Alex seems to be a good fellow and did some tweaks for me on the system I got from him. His prices are pretty darn good, he has things on sale right now, and he's down in Texas, so you're supporting our own guys, if you care about that sort of thing:
My Store
www.aviorperformance.com