The easiest and quickest transfer option is to take a taxi from Santorini Airport to Fira, it's an 8-minute journey that ends directly on the door step of your hotel or accommodation. The fare will be around €30-€35.
Why is taxi so expensive in Santorini?
Santorini taxis are few and can't cope with the demand during the peak tourist season. When traveling via taxi, you don't have to carry around your luggage or your personal belongings. The traffic jams -unfortunately, an everyday thing during the summer months- can raise considerably the final taxi fare.