Zurich is definitely not more expensive than London or the skandinavian countries!
Bahnhofstrasse: From the main station till Paradeplatz you'll finde the usual stores such as H&M, Zara, Mango...Visit Globus department store there and BIG. If you like high-end but not the usual stuff, visit Eclectic Boutique (Werdmühleplatz-off Bahnhofstrasse).
From Paradeplatz till the lake there are all the designers, Prada, Chanel, LV, Bottega Veneta, Dior, Gucci,...Tiffany's. Grieder at Paradeplatz is a department store that features designers (also Marc by Marc Jacobs...)
Niederdorf/Dörfli: More alternative fashion, many skater stores there, but a little off the main street there are some gorgeous boutiques, such as Vestibule (
www.vestibule.ch). They have Marc by Marc Jacobs, 3.1. Phillip Lim, Cacharel, Chloé, Vanessa Bruno...small selection of shoes and bags, as well and some nice jewelry.
On the main street almost at the Grossmünster visit Antares for less expensive but beautiful jewelry and deco articles
Langstrassenquartier (Kreis 4/5

Many streetstyle stores such as Dings (Zollstrasse, featuring Henrik Vibskov, Ivana Helsinki, WESC, Sessun...) and lots of swiss designers (Beige, Amok, Making Things, Chic Happens,...they all have homepages, just google them). Visit Ostblock (Konradstrasse)-eastern european designers and clothes from the great Aleksandra Wisniewska. Visit LuxPlus for vintage and Alex&Chloe necklaces...