While overall computer prices have dropped significantly in that time, Apple has almost doubled what the cost is for the entry internally expandable system.
And yet the new Mac Pro will crush a Power Macintosh G4 in every performance category. And a Mac Pro is cheaper then the majority of equivalent workstations from the major Windows PC suppliers.
Up until recently Apple has always had a midrange internally expandable system.
"Recently" being a decade ago with the G3 minitower (which was the tower), G3 desktop and G3 AIO. Prior to that, Apple had six families (4xxx, 5xxx, 6xxx, 7xxx, 8xxx, and 9xxx) comprising three towers, two desktops, and one AIO. Add in all the clone makers and their products, and the resulting fratricide hurt the Mac's share of the PC market. One of Steve's first steps was to "kill the clones" and reduce Apple's own product line.
There is nothing wrong with the Mac Pro. It is a fantastic workstation and a fantastic deal at that price. But that doesn't mean we should be content that it should be our only option in wanting a more expandable system.
For the record, I believe that Apple should at least differentiate within the product line a bit more.
Instead of a new Mac Tower, just offer a Mac Pro with a single 3000-series quad-core CPU, but leveraging the case and video and drives and everything else. I'd rather see this then a quad-core iMac (ducks the rotten tomatoes from the quad-core iMac fans). And if Apple was really worried about a Core2 Extreme cannibalizing the Mac Pro market to the point it would hurt the Xeon machine, then just ship it with a Core2 Duo and make it the "headless iMac".
I'd also like to see the MacBook Pro (perhaps just the 17") model ship with a quad-core unit to help differentiate it more from the MacBook.
This way, Apple can still leverage the majority of their fixed costs for each form factor to ensure they still "bring home the bacon".