If your payment is blocked later or you file a shipping claim against him.

No other reason to WANT to pay fees.

If you really prefer to avoid it (although this removes your protection too!) you could mail cash.

You find things like this http://answercenter.ebay.com/question/Trust-Safety-Safeharbor/Craigslist-Scam/1000237930

I had a desireable item to sell and (this was in the days when you could see the identities of all bidders on a sold item there) I offered it by email to the underbidder on a similar item. When he agreed to buy mine, I listed it on ebay and he bid on it immediately. Both of us had some protection by going through eBay.

But be careful. He wants to be paid with Paypal?

it did hurt, but i looked at ebay's help and they warned against just such a scam. he said he had listed it on ebay, but he couldn't find the link. that was enough.
i told him i though it was too good to be true and unless he could prove it was legit i wasn't interested. that was the last of the emails, so....