I am sure that you could go to Ephesus cheaper, but as I recall the tour was only about $30. It is certainly a must see, and I would not go without a guide, because the explanation of what you are seeing is a must.
In Greece a city tour to the Parthenon is a must, and again, that tour was reasonable. I was told that the day tours out into the countryside were really not worth it. If you wanted to skip the city tour, you could certainly just take a cab to the parthenon. Afterwards there is an excellent outdoor shopping district (I can't remember the name). Enjoy!!!!!!