I have about $1,500 into my bike, including the cost of the bike (1994 Trek 920 singletrack that I bought at auction for $90).
Here's how my build unfolded:
During initial build, I replaced:
Pedals with metal cage bmx style pedals
Bottom bracket set – replaced with new guts
Seat post with Suspension seat post
Old seat with Cloud 9 seat
Rear wheel with heavy duty rear wheel (48 spoke heavy duty from Staton)
Tires - twice, before settling on the Specialized Armadillo Nimbus tires with spin skins liners – no more flats!
Replaced rear derailleur (that got bent somehow - prior to kit install)
Installed bicycle computer (speedo, odometer)
Installed tach/hour meter
Built and installed headlight system - 55 watt light, SLA battery
Installed Planet Bike super blinky tail-light
Built custom bracket and installed Transit Epic DX Panniers
Installed bar end mirror
And the recent or pending upgrades or replacements:
Stock forks with Rockshox Dart 2 Suspension forks
Front rim brakes with Avid BB7 Mechanical front disc brake
Rear brake assembly with Avid Single Digit 7 brake
Replaced Both brake cables –front with SRAM pitstop full metal jacket
Grip shifters, grips, and cables with SRAM 3.0 grip shifter set
Threaded headset (converted to threadless) with FSA the pig headset
Threaded stem with Sette Edge 2014 O/S Stem 31.8
Handlebars with Sette Duo O/S 31.8 Riser Bar 2014 2 ½” Rise
Brake levers with 09 Avid Speed Dial 7 Levers
Front wheel with Forte’ Terramax wheel with hub for disc rotor
Healight, horn, and kill switch with motorcycle type handlebar controls
Handlebar mount for Garmin GPS
Warner