It's easy to roll your own. I start out with a fitting, measuring you and any of your existing bikes. I build a design in a CAD program to translate your riding preferences and body into a frame design. Next, wespecify tubesets, components, fabrication methods, and finish. After a final review of the specifications, I get to work measuring, cutting, coping, filing, welding, brazing, cleaning...and so on.
The cost depends, no surprise, on the complexity, and no two bikes are the same. Still, as a guideline, a simple fork and frame will run about $2000, depending on the tube set. Adding internal cable routing, internal wiring, hand-cut lugging, and so on adds to the time and hence to the cost.
I source components from a variety of suppliers, and have builder resale agreements with the likes of Chris King, Enve, Velocity, Industry Nine, and others. I like to build wheels in-house to match the bike, but I'm happy to use your wheels or outsource to our friend Justin at Luxe Wheelworks.
A base set of components for a complete build -- using, for example, SRAM Apex drivetrain, Avid BB7 disc brakes, DT Swiss 350 hubs and Velocity A23 rims with a Brooks B17 saddle -- would retail for about $2150 if purchased separately. Bundled as part of a complete bike purchase, I would invoice about $1800. Again, you can upgrade to any degree that suits your appetite and your purse.
In addition to the bike itself, I design and build (or customise) racks and sundry bits that might enhance the ride. In late 2017 I'll be prototyping some new bicycle trailer designs as well, so keep coming back.