We had a taxi last year from the airport to Arillas which is just along the coast from Sidari and that cost us 50 euros. That was pre-booked, I think if you just jump in a taxi at the airport it will cost you more.
You could try e-mailing olgastravel@gmail.com who is based in Arillas and ask her for a quote, she is very helpful, alternatively you could search for a taxi firm in Sidari and try getting a quote from them.

It's always better to book a taxi in advance from your resort. Last year, Alfa Taxis and Roda Taxis were charging 44 euros for each transfer of up to four people. Transfer time is about 45 minutes and they are very reliable - definitely better than a coach! To find their links, have a look at the official online Roda website.

Steve

booked taxi for june for two 45 euro one way to sidari