D2xs are going for about $1500-1750 (as far as I can tell)
D2x just around a grand
D3's are about $3300-3500; some just around $3k.
Used D700's (considered pro by Nikon) are going for $2100 or so (which is stupid since new is about $2400!)
The biggest drop looks like the D3 - I'm thinking of jumping on a used one, I feel the price difference between a new D700 ($2400-2600) and a new D3 ($3k) is SO MINIMAL for the,
1. 300,000 shutter life
2. 2 CF cards
3. Faster AF
4. longer STOCK battery life