Forget LoWu if you are willing to go to Shenzhen, go to the electronics area which is several subway stops away from LoWu. Everything there will be way cheaper than HK, Europe, or the US, but everything there requires serious bargaining, and once you pay for it, you own it, no matter what happens -- so you have to check everything in detail BEFORE purchase.

Note that you need a China visa to visit Shenzhen.