Yea, that's a bit optimistic.
I think it's just a figure of speech in most cases. Some say 'building up' a car. I think 'built not bought' refers to someone getting a bone stock (or close to) car and adding the perfect recipe of go-fast parts and such to make it what it is, instead of buying someone elses car that has already done all the modifications and you just need to buy it, put the key in, and race it.
I would not say i've 'built' my M3, but I've built it up to what it is today. I chose all the modifications that I wanted, as opposed to buying something that someone else put together. My car was mainly stock and I added the following:
TCK DA suspension with TCK Camber plates 400f/500r
APEX Arc-8 wheels with 255/40/17 Star Specs
10mm front spacers
Motion Motorsports Underpanel
Stromung cat-back exhaust
3.38 final drive diff
Shark Injector
28mm front sway bar
JB Racing LTW flywheel
Sachs Race Engineering Pressure plate
M5 Clutch disc
Short Shift kit
AKG DSSR
CDV Delete
RTAB Limiters
Poly FCAB’s
So, I didn't 'build' the car, but every single one of those modifications I bought and installed myself, and never paid someone else to do it.......
.....so not sure what you call that, but I think that is what some of these guys are referring to.....:shrug: