Bus is the cheapest way to come to Benidorm from Alicante Airport, 7€ per person (+2€ if passengers travel insurance wanted). But only four buses are available (09.15am - 13.15pm - 17.15pm y 21.15pm to Benidorm and to the Airport at 08.00am - 12.00pm - 16.00pm y 20.00pm), seven days a week. Bus stop in Benidorm is at 'Centro Comercial La Noria' in Avda. Europa and just in front of 'Arrivals' at the Airport.

Alsa is the company which negotiates transfers from Airport-Benidorm-Airport. Underneath you can see their web page (available in english) where you can book online. A great feature is receiving your reference number via cellphone (if you want to), so only show the driver your mobil screen and what's it. I've booked online a few times and everything went without a problem. Two things to remember: 1. care your batteries  2. times shown up on the Alsa web are local time.