[nextn]

You don't permit ticket transfers. Instead you sell tickets back to the venue for the price they were bought. Your tennis buddies would better be ready to buy the ticket from the venue 1 second after you sold it back to the venue, else someone else might get it.

Scalpers can't transfer tickets in this system.

[Incipient]

I was thinking this, however you "transfer" to the other person, the original buyer gets a refund, and you pay the original ticket price+tx fee, or original buyer pays the fee. Either way.