Sounds like a fair price to me. You can do an advance search on ebay and click on completed items. This will give you the final price of the searched item. See what they are selling for there. Do you know what the computer was used for ie. processor intensive tasks, was it used on the road, or mainly around the home, what is the battery like, and general wear and tear. You can also check how bright the screen is set for. The lower the better. I do remember some of the 1.67 GHz Powerbooks have screen problems. (17inch) Vertical line etc.

Here is the official Apple problem list for the Powerbook.

http://www.apple.com/support/exchange_repair/powerbook.html

Without Applecare, you will pay dearly for any repairs. Under Applecare, Apple can charge $670 for a $70 repair and say it is free because of coverage. You come in without Applecare for the same $70 repair problem and get charged the $670 based on their repair charge history. Non-Apple repair places do the job for half and still make a profit. A Powerbook without Applecare is worth half of what anyone wants.

As the economic downturn worsens, boys will sell their toys for 25 percent less in three months and 50 percent less in 6 months. Waiting is good financial sense.

Better yet, recycle an oldie from the dump, get a donation from a friend or a rollover from a school to use with Linux for the next year or two while you add to your $600 stash and then get a new one.