How do people on ebay get thier cell phone ect. products to sell so cheap? -

I go on ebay and buy cell phone chargers and such and I just want to know where they get the stuff at and be able to sell it so cheap? Do they buy like thousands of dollars worth and make profit or how does this happen. I see that people from Hong Kong sell alot of things like this.

either buy in extremely large bulk or stolen goods - either way it makes it very difficult for the average person to make a buck