The memory alone costs about $250 new on Dealram.
He also said "1.4 TB HDD's" which I assume means two of them (and probably 1.5 TB as I've never seen 1.4 TB). Those are over $100 each new on Pricewatch.
The Pioneer DVD DL is worth about $50 if you consider the brand name.
So that's around $450 - $500 in upgrades.
Thats all very true, but the system as a whole isn't worth that much. Sometimes it makes more sense to part out a system than to sell it as one unit. If it were a quad 2.5GHz or even a highly desired DC 2.3GHz model (because its the fastest to run without the liquid cooling) the price is higher. If he can find someone to pay that much, then thats great. But with brand new Macs and even faster G5's for around the same price or less, its a hard item to sell for what it may be truly worth.
Sure, yeah. If $500 in upgrades only added $200 to the selling price, I would strip it down to base, sell the upgrades separately then sell the G5, get some more money that way.
A system, or any item, is worth however much someone wants to pay for it. If someone pays $1500, then it is worth $1500. If someone would only pay $500, then it is worth $500. It is up to the buyer and seller to negotiate a price on which the two parties can agree.
What if one person wants to pay $500 and another person offers $1500? Is the machine worth $500 or $1500?
Just because someone has some kind of temporary mental problem and pays $5000 for a G5 doesn't mean that, for general purposes, the G5 is worth $5000. I think we could all agree that a base spec working condition dual G5 at this point in time, is for general purposes, worth more than $1 and less than $5000.