I have used paypal a lot...both for sending and receiving money.
I would recommend contacting some of those that have dealt with him and find have someone that can vouch for him over PM.
He is likely either using paypal credit or he just has a lot of paypal funds...but as long as he is sending friends and family, you should be good.
I would recommend doing it unless you get an uneasy feeling.
Of course, if it is a sought after pin at a reasonable price...if you aren't confortable, you can always go to the next buyer.