Hmmm, i looked into having an Inconel made for my Caterham R500 some years ago and found that it was some 8 times more than stainless steel. This would have been around £ 5K for my system, second problem is that it is prone to cracking around stress areas like collector boxes and manifold joints and requires carefull design so that it does not flex putting undue strain in these areas. Also trying to find an engineer shop to bespoke make the manifold flange was difficault because no data existed for my engine. So in the end it was just not viable because it offered no power gains and the weight issue was not worth the cost.
If you want the dogs exhaust then try Inconel - Wikipedia, the free encyclopedia As said as its used in F1 for exhaust etc.. But can brake easily
Still would have been cool but if your R500 engine vibrates like my tiger does it would not last 5 mins
I don't know how you post the actual clip up, so here is a link: Yamaha YZF R1 2008 black on Fuchs dyno. - YouTube