This is from a UK perspective as it's only ebay UK that I monitor. I don't intend this thread to be a "here's a cheaper one->>> url" discussion, but a high level view of how ebay pricing reflect demand and supply, and the number of people buying the n900 who quickly sell it on.

When the n900 was first on sale, there were rarely units on sale, perhaps one a week, and prices were close to full retail list price of £500. Items are typically new in box.

It took about a month for there to be significant numbers offered and prices remained solid right the way to Christmas - typically £450 and up, depending on the seller's reputation. Typically a few items were listed every day, most were either new in box or slightly used. Items attract bids even at £480.

Soon after Christmas, and particularly in 2010, numbers offered increased, and start price fell, by the end of the first week of January, some sales reached only £425. More of the devices are lightly used. Items over 475 attract few or no bids.

By the end of the 2nd week of January, starting prices have fallen to as low as £300 and closing prices have fallen to about 400. Items listed for over £440 do not attract many/any bids.