That's almost $95 cheaper than any other online hotel booking website that I could cross check prices against. Booking.com, Hotels.com, Expedia.com.au and even The York by Swiss-Belhotel's own website were all charging the exact same amount of $520 (or $260 per night). If you're flexible enough to stay during the week the prices are quite a bit lower as I see making a booking for Monday and Tuesday nights that week (26th and 27th of August) will cost you just $376.34. These are good rates for a hotel of this class and location in Sydney.
Important: to get the above mentioned rate you need to do two things - (1) apply the 10% off promo code for HotelClub (found on Buckscoop's Voucher page) and (2) make your booking via HotelClubs mobile application for Android/iOS devices (or more conveniently book using your computer with the method described in my recent blog post about their mobile app).