Did some gear shopping, and I must say that Wing Shing / Tin Cheung's prices are getting relatively uncompetitive as compared to the local stores. I don't speak Canto, so naturally I was earmarked as a tourist. I walked past some of the price.com.hk stores, and some of them look really dodgy - so you'll be sorely disappointed if you use these prices as a benchmark.
Eventually I bought my gears from Tony Leung at New Sanyko: some of the CSers are regulars there, and I got a "local" pricing, which is pretty decent.
An alternative to payment is actually to withdraw via DBS ATMs in HK. Just make sure you set sufficient withdrawal limits via Internet Banking. While there is no service fee, you'll get FX charges. For instance, I did a cash withdrawal to test things out, and I was charged at 5.996 vs the Arcade money changer at 6.15+. Hope this helps.