Well, pound for pound, BT pipes are probably the most expensive. As they should be. BT's history is building race pipes for the fastest bikes on earth. And he's been very sucessful.Not that I own anything special, but it's hard to believe that mild steel would be the go-to material for pipes of that caliber. I mean, who would drop a grand or two on custom pipes just to watch them rust away. Sure, you could ceramic coat the inside, but it still seems odd. $0.02
The reason for mild steel pipes is because they're the best for racing. Titanium pipes are lighter, but they don't last. I'm guessing stainless pipes were never a part of BT's repertoire.
So, what do I do? Send him an email asking him to make stainless pipes.