Comfortable accommodation in May for 2 persons can be found for between €40 and €80 per night. A meal for two that includes a starter, two main meals, salad and a litre carafe of local wine will cost you around €25-35. This can vary widely depending of level of establishment you eat at. A cheap vegetarian dish (pulses or vegetable) will set you back by no more than €5-6 a plate. If you get your breakfast included at the hotel, that is good because breakfast can add another €15 for the two of you per day.
The only ferry from Kusadasi to Greece goes to the Greek island of Samos. It’s a great island and certainly worth a few days. From Samos, there are usually direct ferries to Mykonos and Syros. These are very different islands that have a very different vibe – but both appealing in their own way. From Mykonos there will be direct flights to Western Europe (most likely Rome, Paris, Amsterdam, and London) though not every flight flies every day so requires some planning. Santorini would be another ferry ride from Mykonos. And Crete farther still. So you wouldn’t have time to get to either island.
Since airline reservation requests are often made by city-pair (such as "show me flights from Chicago to Düsseldorf"), an airline that can codeshare with another airline for a variety of routes might be able to be listed as indeed offering a Chicago–Düsseldorf flight. The passenger is advised however, that airline no. 1 operates the flight from say Chicago to Amsterdam, and airline no. 2 operates the continuing flight (on a different airplane, sometimes from another terminal) to Düsseldorf. Thus the primary rationale for code sharing is to expand one's service offerings in city-pair terms to increase sales.