in reality you are pretty fucked, as said ebay/paypal sides with the buyer almost always since the buyer can just do credit chargeback or bank reversal and ebay definitely isn't eating the losses, so the seller gets fucked.
its part of doing business, just like if you run a store you have to deal with shoplifting and employee theft its something you have to deal with as an online seller. assume 5-10% of your sales are fraud and budget accordingly. only ship to verified paypal, set the checkmark on ebay where you don't sell to people with more than 2 negative feedback, etc.
now you can pour an infinite amount of time and effort into dealing with these guys, but chances are they really won't give a shit. you could get a lawyer friend to write up a threatening letter, follow it up with a police report in their county and yours for fraud (across state lines) and send them a copy of the report. in reality that won't do shit since the police don't give a fuck but some people will get a little scared.
if you are really into it you can file with a debt collection agency, you basically pay them to go get the money and they will hound the person endlessly. again, nothing really done but you are outsourcing harassment.
i mean you could get into shit like hiring locals to go threaten the guy or do it yourself with a gun but at that point you have crossed the legal line and the blowback will probably be severe if things go wrong. Legally your options are hitting them with lawyer notes, police report, putting a mark on their credit history.
Keep in mind when you start stooping to a scammers level, you never know what kind of crazy ass shit they may do back to you.