Sounds like he's trying to pocket the profit from the eBay fees by avoiding processing the payment through them. The way he is doing it he only has to pay the paypal fees.
I'd tread with caution and talk to eBay/Paypal as you don't want to get in trouble because he is trying to do the dodge.
Buying an item you've already brought or discussed buying on eBay through other means (even just through paypal) is against eBay policy so you don't want to innocently be pinged with a mark against your account.
Good luck with it.