I'm going to say they're overpriced but that's because I'm not into fashion so I see almost all branded products as overpriced. The only clothing I spend a lot of money on is sports clothing, so for me that would be hiking, climbing & running. New walking boots cost around £120 for instance, I could probably get an unbranded product for half that price but it wouldn't be as good.
The thing about Jack Wills is you pay a huge amount for the name, and fashion prestige that goes with it. So for someone who's into fashion it's probably worth it, for others definitely not.
You're looking for different things. If I buy a North Face jacket, I'm buying it because their waterproofing & other technologies are superior. If you buy a Jack Wills hoodie you aren't buying it because you want to be warmer (you could get a non branded one for that), you're buying it because you think it looks good and its fashionable.
Depends what your priorities are, personally I can't afford to spend so much on my clothing.