Besides the main categories mentioned above there are several other special structures and materials which are of course reflected in the string price. First there are strings with textured surface designed to add spin to your shots. But unfortunately those textures become smooth with play, and they are also lowering the string durability. Plus, Babolat DF Rough, TOA Geo 66 . Then there are some monofiber strings made of special materials brought to you by Cannon , like the famous Big Banger, Distance, Silver String .
Durability is said to be outstanding.
Unfortunately I haven't yet made any experiences with those strings. To absorb string vibrations some manufacturers fill their strings with oil . Those strings have in fact a very unique performance. Whether that's positive for you or not you should find out in your own test. Gosen Vibless Plus .