it generally costs more - companies just get such discounts on components it's difficult to match the deals they do - for example, on my Dolan, if i'd have been happy with the components that were on offer on one of their fixed builds I'd have been able to get DI2 Ultegra for the price of the normal Wired one...
On the other hand, I know that every component on my machine is exactly the one I wanted, not what some product specification manager could get a good deal on. For a self confessed picky so and so like me, it was probably worth the extra £3-400 to get exactly the right crank lengths, stem raise, length,bar profile,materials and so forth...
With some astute purchasing and a unhurried approach, it's possible to pick up bargains on kit - for example there'll soon be a glut of 6700 ultegra on the market as the 11 speed is rolled out by the big S!
I have to say, I'm currently working on a 'crosser as a sort of do-it-all bike - stick guards on in the winter and use it as a roadbike, knobblies in summer for the offroad stuff around home that i'm currently completely overbiked for on the Inbred 456... Problem is, I dont want an Alu frame but do want to be running discs, but most of the carbon jobs don't have mudguard drillings/eyes and the Ti Lynskeys are a bit out of my budget for a winter hack and summer joyride bike...
