I'm assuming that - if you're not long-term or regularly in China - the opportunity cost of time will be relatively high to you. Lack of abilty to communicate and being generally unacustomed to this environment raises your costs even higher.
It's fine if you're casually shopping. But it will not likely get your specific high quality rep you want. But then again if you're a serious headcase like many here you might as well fly to GZ just to do that.
Personally, I would take retailing on the GZ market over online shopping any day. Besides being able to physically inspect the goods, most importantly I'm afraid of customs risk. And since I'm there at least once a year I can avoid that.
edit: ok obviously most orders to europe are sent via CN-UK-your destination
Ive actually never ordered online. I fear for a complete loss + possible fine if my parcel is inspected. According to a documentary I've seen, every single air parcel to Germany is to be opened and inspected - no exceptions. Well in reality, some seem to slip through. From my personal experience, MOST packages I receive will have been inspected. I just find it too risky.