In the middle of the perfect lighting condition day, you are correct - the high end scopes doesn't do much more that the mid range, $1500 scopes. But in bad lighting situations, the high end scopes shine vs the mid range scopes. The high end scopes continue to provide sight pictures that allow accurate fires on properly identified targets, which you can't confidently do with the mid range scopes.
An example of this: at the Alleghany Sniper Challenge there is a stage called "Heart of Darkness"... its a >1000yd target sitting in a very shady, deep hollow in the ground. I was up there in poor weather conditions: foggy, rainy, generally low lighting. The guys running Benders and Premiers could see the target and, importantly and challenging, splash. Most of these guys made 2nd round hits - see their splash on the first round, make the correction and sent it. Most guys running the mid range scopes did not have similar success.
That is what the additional $'s are buying.