Some items in China is much more cheaper than in Taiwan or USA.
Though it can be easily baught via Taobao but Chinese/Englsh is not everyone's mother ton. Build an open source group-buying website
I've built one for people in Taiwan to buy mountaining gear in an outlet in the US and ship items to Taiwan. It helps people save money. I provide this website for free but I earn some money from my credit card company.
Hope it will be come next osCommerce !
Here's the sample : http://cgearc.com