I share your frustration to a certain extent. There isn't always a buyer for every seller, but there are enough people willing to buy at a given price to make it worthwhile for some. This only part of what makes eBay such a success.
I shake my head whenever I see PowerPCs in awful condition -- missing HDDs, cracked displays, not known to work and missing an AC adapter/battery, and on and on -- offered at a premium. Whether or not it's by design, many of the PowerPC ads on NYC Craig's List are misleading in that they never mention that the hardware and much of the software is unsupported and not useful for many tasks. This may be a gray area in person-to-person commerce, and there will forever be opportunistic people who cash in on buyers' ignorance.
I bought my iBook for $200 three years ago in pristine condition. If I were looking to buy today, I wouldn't pay half that price unless I had a compelling reason to do so. My sense is that PowerPCs have reached a plateau in terms of price/worth. Things get old, and they start breaking down, even with the best maintenance and care. Unless you're a collector, someone who wants to play around with a PowerPC, or simply unaware of what you're buying, I don't see many people paying a premium as was the case just a couple of years ago.
I've kept my iBook in very good condition, and treated it with the same TLC as I've done with all my Macs. When I sold Macs in the past, people were universally impressed with their condition, to say nothing of receiving hardware upgrades, original packaging, stickers and original discs. I always got a price I thought was fair, and no one ever felt cheated.
I could probably get a decent price for my iBook were I interested in selling it. But I'm not. At this point, I'd much rather keep it, regardless of if/when I upgrade to an Intel Mac. And I just don't see the point in purchasing another PowerPC. I've done my time optimizing my older Macs, and have since reached diminishing returns in terms of keeping things current.
Phoenix CL is the same. Some jerk is selling the first macbook and trying to get $300 for it by saying "runs the most current MAC OS," puts the wrong year, and also has a HDD capacity that doesn't match any of the macbook configurations. He/she also put up a stock photo of it with the OS X Tiger desktop. I was initially interested, but if I'm going to be stuck at OS X 10.5.8 or 10.6.8, I might as well not waste my money "upgrading."
I think I'll always keep my iBook and when it starts to become less and less useful, I'll just modify it like crazy.
1. remove airport card, dial-up slot and modem hardware.
2. Install a usb hub and solder it to the board.
3.connect and place a wireless n usb stick(without the casing) inside the machine and find a way to fill the dial-up slot with a usb port.
2. remove ODD and put in a media-card reader and try to find a way to install a mini dvd system(probably not possible)
3. definitely getting rid of HDD and going with either a SSD or something similar but smaller perhaps. I considered compact flash.