Every country is represented on Ebay and anyone with a computer and an internet connection can sell on ebay.
I know many people from many different countries that sell on ebay. Just because you live in one country doesn't mean you have to sell to that same country. ie: I live in USA but I sell to Canada, UK and Australia.
I'm not Chinese and I don't do much selling on Ebay anymore but I know several people making a full time living on ebay.
i live in Malaysia but i use dropship service from China. I know some my friends from US and AUS buy bulk from China and selling back on their market.
The cheapest gadgets are in China, so I guess, there's a ton of Chinese selling on eBay making premium bucks!
as a US citizen I'm sometimes hesitant to buy items from ebay sellers from China, so I think it's really important to ensure proper delivery and offer guaranteed arrival