I'm not saying you're not who you say you are or don't have the credentials you say you have, I'm saying that I (and we, as in we on this forum) really have no way of knowing about you besides what you tell us. I don't mean to put down your business or your crank or whatever, my point is that a Nissan crank carries with it a more well-known seal of quality because of the name attached.
Your stuff may be really good, I don't know, but a lot (read: most) people will be kinda sketched out about paying $600 to someone they've never really heard of for such an integral part of their engine. This isn't, like, a muffler or something, if the crank isn't perfect in the slightest little bit it would basically destroy your motor. You said you have nothing to prove; I'd personally want some proof of quality and reputation before I spend $600. That doesn't really matter much since I'm not in the market for an RB24DET stroker kit, but I know I'm not the only one who feels that way. Losing nearly 2 grand on a shady internet deal will do that to you
Anyway, maybe you're not some random dude selling cranks, but when you see a post that says, in short "hey I've got RB24DET stroker cranks cheap, $600, who wants one?", what else are you supposed to think? =P