Well, I'm not making a case for those prices and I'm wondering about all the tinkering that seems to need to be done before these things are "turn key" but, if they're making a living doing it, I guess there's a market for it.
Now, putting things into perspective, think about your refrigerator repair man. How much does he charge you for labor to install that .50 o-ring or that $5 defroster strip? If everyone knew how to repair their refrigerator, he'd go out of business and if everyone knew how (or wanted to) build one of these bikes, Ridley would be selling high end cooking cutlery or something like that.
They do have some nice looking stuff on their website. Oddly enough though, I'm not sure they show a COMPLETED bike on the website. I could be wrong but it struck me odd that they don't show a bike with the throttle and clutch, fuel hose hooked up.