What's the difference a budget and a top-of-the-line precision steel rule?

Over at my other website, Cool Tools, we just posted a new video produced and hosted by my old MAKE colleague, Sean Michael Ragan, about steel rules. I had my doubts that a 10-minute video comparing 6-inch precision steel rules would hold my interest, but it did! Sean looks at rules under a microscope and points out the differences between three brands of rule. I would have thought the cheap General tools rule would be about as good as the Starrett that costs four times as much, but Sean's video convinced me that it really is worth spending the extra money for the Starrett.

Tools (Recommended):
Starrett C604RE-6 6" Rigid, US Units (4R - 1/64", 1/32", 1/16", 1/8")
Starrett C636EM-6 6" Rigid, US/Metric (36 - 1/32", 0.5mm, 1/64", 1mm)
General Tools 676 6" Rigid, US Units (4R - 1/64", 1/32", 1/16", 1/8")
General Tools CF667ME 6" Rigid, US/Metric (31 - 1/32", 1/64", 0.5mm, 1mm)

Related tools mentioned:
PEC Tools 402-006 6" Rigid, US Units (4R - 1/64", 1/32", 1/16", 1/8")
Starrett C304SRE-6 6" Semi-Flexible, US Units (4R - 1/64", 1/32", 1/16", 1/8")
Starrett C304R-6 6" Full Flexible, US Units (4R - 1/64", 1/32", 1/16", 1/8")
General Tools 616 6" Flexible, US Units (4R - 1/64", 1/32", 1/16", 1/8")
PEC 262-006EZ 6" Rigid, Black Chrome, US/Metric (31 - 1/32", 1/64", 0.5mm, 1mm)
PEC 262-006TN Tools 6" Rigid, TiN, US/Metric (31 - 1/32", 1/64", 0.5mm, 1mm)

Image: YouTube/Cool Tools