When it reaches 200, buy...

Here in the US/Ebay nothing is closing under $500 for unlocked n900s. Given a New In Box one is $550 (amazon) or $540 (dell) that seems about right.

Perhaps some of these UK ebay'ed ones fell off the back of a truck?

Remember with ebay, you never know what the reserve is, so even if they're listed dirt cheap, does not mean they sell them at that price.

Seems odd to lose money on a phone you could return for a refund, doesn't it?