I would find it so hard to judge what is considered a reasonable price on a forum such as this that has a worldwide audience. There would be so many different factors influencing the price, including how many other people in the area are also selling, either used or new, and the economic demographic of your area.
Where I am near Cupertino, CA with so many people working for Apple or related to people working for Apple, there are a ton of early adopters here. People know more than just rumors which you find on these boards, but for obvious reasons, you don't have them telling the world. However, in small circles locally, people talk about their work, which often on some level includes Apple, and when a "new" product comes out, it's not so new to us high tech in the valley or nearby.
From what I have experienced, the early adopters often have more money than most to spend on high tech or are simply in a high tech lifestyle and have apportioned funds accordingly, and have no issue with selling a still perfectly workable Apple product, still on warranty,
on the cheap.
If you see local ads at any Silicon Valley area colleges, laundry businesses, post office posterboards, or almost anywhere, people dump relatively new Apple gear very cheaply since most are on the hunt for the flavor of the month.
Where some of you may find you Mac to be some sort of investment, being so close to Apple and seeing the company through its ups and downs, most locals see a computer/iPod/iPad/iPhone as useful tools. You buy it, you use it, and when you sell it, (like any useful tools), you probably don't have a strong resale value. If you want a good resale value, get into baseball cards or the "hot" antique item in favor.