Well, bar perhaps ME2 and the Ninja Gaiden games, I've seen most of those consistently go for a great deal less. Just off the top of my head, the last 2 or 3 Survival Editions I've seen have gone for around $400-$450. You can see the one that just ended posted on the rare finds topic ($355 WITH extras):
http://www.ebay.com.au/itm/221043270...84.m1423.l2649
Also, every time I've seen a Fortune Hunter's Edition up it's been anywhere from $2500 to $4000. Realize that searching eBay you may FIND a lot of extremely high prices, but that doesn't mean that's what they're worth or what people pay for them. As a general rule of thumb, don't look at current listings to see what things are worth; look at completed listings.
And what Assassin's Creed 2 edition are you talking about? Master Assassin? White Edition? I haven't seen either of those sell for $400.