wrong
basic G4: $1,299.00
Basic G5: $1,999.00
Top G5 : $2,999.00
Of course you can make them a whole lot more expensive, maxing out the 8 gigs of ram, getting a 23" cinema display etc...
And like LiC said, OS X is completly new while XP is win2k with a million more lines added to the code. And you do have classic still, all the apps that need OS 9 will load up in classio.