I don't know how fast a 600Mhz PPC powered Amiga will run, but what I suspect is somewhere close to a bottom of the range Celeron or Duron. Ofcourse there is no real way of finding out as there is no dual OS software that could tell us, and even if there was, programming/compiling inefficiencies on one platform or the other could end up hexing the whole test - so bottom line is even if we had, say, Lightwave 7 for the Mac, PC and Amiga (I know v7 wasn't released for the Amiga, this is just a supposition) and rendered the exact same project, we still wouldn't know what "processor" was faster, because each of the different platforms uses a different set of development tools.
So is the 600Mhz A1 a ripoff? I don't know, because no one apart from Eyetech knows how much they are paying for it. Also it could be that Eyetech themselves are being ripped off - and are simply passing the price gouging down the line.
What Wayne says is true about the Amiga however. Amiga dealers have a long history of selling standard computer hardware at inflated prices. Even when Commodore were in power I never bought simms or hard drives from an Amiga dealer - I never have been rich enough to pay twice as much for something, just because it would fill the wallet of an Amiga dealer, instead of giving a marginal profit to a PC dealer.
I think $600 for a processor/mobo combo is a hell of lot of money (the 411 was in UK pounds Wayne, so add 1/2 that much again for the pound/dollar conversion) - especially considering that a 1.2Ghz Duron + mobo can be bought for under $200, and usually includes sound, graphics, modem, LAN and USB onboard. However it is in keeping with Amiga history. Hands up who paid $600 for 1/2MB A500 or worse, $3000 for an A3000.
The closest thing the Amiga has ever had to a value for money computer was a toss up between the A4000 '030 and a bog standard A1200. They didn't have the monitor, as much ram or as large a hard drive as the similarly priced 486DX (A1200) or 486DX2 (A4000), but they did give about the same performance for a similar price.
I personally think that if CBM had priced the A3000 at the same price as a 386DX - which was it's main competitor at the time - they would have won the business world over in about a month. Missed opportunities are the one constant in the Amiga's history, and it never ceases to amaze me how often they were missed.