Hmmmmmm. Let's see.
Mac OS V 10.3 ~$180-200 plus 4 upgrades in the last 3 years.
Windows XP ~$30-90
Case closed.
Hmmmmmmm. Let's REALLY see with the actual facts instead of prices you made up!
In the Mac world
Mac latest version OSX OEM free with any Mac purchase.
Mac OSX.3, retail price = $129
Mac OSX.3 five license "Family Pack", retail price = $199.99 or $40 per computer.
Upgrades
Upgrades from X.0 to X.1 = free!
Upgrades from X.1.0 to X.1.6 = free!
Upgrades from X.1 to X.2 = $129
Upgrades from X.2.0 to X.2.8 = free!
Upgrades from X.2 to X.3 = $129
Upgrades from X.3.0 to X.2.8 = free!
Each .1 step includes MAJOR software upgrades and NEW applications easily worth the $129. Each .x.1 step includes security, speed, and application enhancements. That's 25 upgrades of whoch only two were charged for.
In the PC Windows world
Windows XP Professional OEM suggested retail $199.99
Windows XP Professional OEM street price $129.99 - $159.99
Windows XP Professional suggested retail $299.99
Windows XP Professional Upgrade suggested retail $209.99
Windows XP Home Edition suggested retail $199.99
Windows XP Home Edition OEM suggested retail $129.99
Windows XP Home Edition OEM street price $59.99 to $79.95
Incremental upgrades = free!
CASE CLOSED
You're the one that's made up prices, but you can have the last word on that one. It doesn't really matter, since the Mac is dead at most real companies.