It's not the cost of replacing batteries it's being able to leave it on and knowing you're gtl, i mean gtg
A lot of people believe Aimpoint to be much more rugged as well. Plus EoTech had some issues with batteries bleeding off.
I forget to turn optics off quite a bit. The xps turns itself off the Aimpoints just keep ticking. The Eo went close to three years on one battery. I imagine that's good enough for most of us.