On ebay, sellers can set whatever shipping rate they want. As a result, many will set very low prices to get your attention (and move their items up the list), but you still end up paying the same (or more).

This merchant you mention is doing just that. They will not sell it to you for $20 for a local pickup. You need to look at it as $120, shipping to US included. If you want to ship to China, you need to negotiate with them.