The only time I noticed the difference in quality of glass was when I was ground squirrel shooting! On the days when I had the cheaper glass up my eye was pretty tired at the end of the day, 8 to 12 hours out in the field usually looking through the scope. On days when I had the better glass my eye was not as tired. So I usually buy once and cry once!
I have noticed that I usually have about as much in glass as I do in the rifle. Did not plan it that way, just something I notice after the fact.