here's what you do:
put some speed holes in a cannondale
lace your wheels with 4 spokes
ride on bare rims
duck tape a piece of wood to your fork crown for a handlebar
instead of a seat and post tape a piece of cardboard to the top tube
file half the teeth off all your cogs
you don't need bearings
^there's a whole thread with stuff like this^
the thread title should be changed to "i want a fixed-gear for less than $1000"
seriously, most fixed-gears with modern frames are 20 pounds or less.