[octaviancucu]

I've read that the easiest way by bus is to take THY bus from the airport to downtown Izmir (hotel Ephesus), then a taxi to the Main Bus Station, followed by a direct bus to Kusadasi.

The prices are 6, 5 and, respectively, 20 USD. Are this information still accurate?

[Umit]

yes, approx 20$.

then a taxi to the Main Bus Station

You can use public transportation system instead of taxi.

[octaviancucu]

Taking into consideration the luggages we will have with us, I think we will hire a taxi from a turkish travel agency (Sisan Tours, I think), but we still have 2 weeks to think about it.

[Kusadasihopeful]

the best way to go would be to take the hava bus to the effes hotel in izmir . across from the hotel u will find the bus companies have ticket offices where u can buy your tickets and take the free service bus to the outogar to catch the bus to kusadasi
regards