The Apple cases feel great in a way that 3rd party cases do not.
I have been buying Apple cases (leather, then finewoven, not silicone) since they started, whereas my GF chooses some random 3rd party case that catches her fancy, and, IMHO, the Apple cases are just so much nicer. Feel good in the hand, thinner and lighter, small details that are barely noticed but matter (like how the buttons feel), and are well worth the price.
As for Finewoven, I don't know. Maybe other people treat their cases really badly, or often get them wet or something?
Maybe I'll be singing a different tune in a year, but after, what, 6 months or so of use I still love my Finewoven case. It feels even better in the hand than the leather case, and I see no signs of degradation.