I bought a domain from a seller that lived a few minutes away from me and he offered to meet and I could pay in cash. I didn't see the point myself, so I just politely declined and sent PayPal.
I have always liked the idea of face-to-face domain sales. I was thinking more of a retail domain store, maybe in Time Square, New York... You just walk in and all over the walls are little cards, each with a premium domain name printed on them. Each one also has a price tag. You pick one, walk up to the front to pay. The cashier would say "oh, Hypothetical.com. Nice choice. That will be $8,500." You pay they do the transfer on their end, they write the name on a piece of paper and hand it to you. "There you go, have a great day!"