eCost sells a Power Mac G5 2.5GHZ Dual Processor (only 512 Mb RAM) for $2,994.00
Monarch Computer sells an Athlon 64 3500+ (the 2.2 GHz CPU) for $1,085.00
Uh, not quite... that quote is for the SINGLE processor version, no Operating System, no software, no keyboard, no mouse, onboard sound, minimalist video, no modem, no NIC, No Firewire, no speakers.
After building one up as far as their build would allow (still only ONE [1] processor) and NO SOFTWARE equivalents... the price is $1944.97.
If you upgrade the MB and add the second Processor, guess what? The price is going to be close to $3000 and STILL NO SOFTWARE!
And if you did build out a dual CPU system of closer to the same speeds, then the performance difference reported between the Mac and Athlon would evaporate.