There are relatively rare random attributes for items (such as the suffix 'of angels') which increase their value to merchants, but do not give any other bonus. This works best when you find such items and sell them (some people have wondered if they should buy such items; since if they are that expensive they figure they might have some kind of hidden attributes or benefits).
An interesting find in the wastelands, worth 50,000 gold (I assume the 'silver' part is what bumps the price up);
Silver Long Dagger Of Mater Warriors
Durability 10
Damage 9-31
+4 Strength
I really need to get to the wastelands it seems.
