We're talking bespoke frame-building, right? With almost unlimited possibilities, the exact cost of a project will depend on build specification. That said, a custom-built frame set can be built to a set specification and price:
Fast Road or Super Audax frame and fork from £950: fillet-brazed fast-back Columbus Zona tube set, Columbus SL fork blades, double water bottle bosses, stainless steel head badge and gear cable rubbing strips and one-colour paint finish including down tube decals.
Can be fitted with a Columbus Minimal or similar carbon-fibre fork - please ask for details.
Road Tour or 650B frame and fork from £1150: build spec. as standard Fast Road frame and fork, with cantilever brake fittings and mudguard and rack bosses.
Bi-laminate bottom bracket - add £200
Bi-laminate main triangle - add £200
Part-polished stainless steel fork blades, rear stays and dropouts - £300
Many other options including hub gearing are available; please ask for details and prices.