An “early-bird ticket” is a ticket purchased far in advance. How would you say “early-bird ticket” in French?
I've seen and been to multiple conferences in France offering early bird tickets. None of them bothered to translate the word in their French descriptions.
As far as I know, there is no strict equivalent. A ticket en pré-vente or pré-réservation doesn't really convey the fact that it's purchased months and months in advance, possibly without even knowing the programme of the conference or event. And to me, pré-vente is generally meant as opposed to sur place (on location).
As said in Antzi's answer, Prévente or Pré-vente are good.
I would prefer when possible Pré-réservation ("Pre-booking"), a booking being most of the time nothing else than a sale in advance.
Réservation à l´avance is also usual.
For purchases one could use Pré-commande.