Why is the insurance so much higher on progressive if my eye doctor specifies progressive? Read on for details. I will award best answer.?

Early last year I stared working for a major company which offered vision insurance. I'm 55 years old and wear progressive glasses. I have a simple prescription. (od or right -1.00 -050 090. os or left -1.50 0 0 with +2.50 add) Since I had vision insurance until the changes kicked in during April I checked into getting a spare pair. I was told by the optical store that the copay was 80 to 160 dollars on progressive or 10 on lined bifocals which I don't want and can't get anyway because of the eye dr. writing progressive on my prescription. I don't understand if a medical professional specifies something why the co pay is so much higher? As a result I did not take vision insurance which was only about a dollar a month. I should have took it for the 10 copay on the eye exam. Anyone else have this experience?