Yeah, when you get up there in devices, the battery cost explodes! Actually, there is a small hit for wired devices as well. I believe around ~.5 - 2 watts per device! That can add up as well. The more we add, the more the law of diminishing returns apply.
I ended up hard-wiring some of my troubled sensors and just outright replacing others. I had some Visonic Contacts that were chewing through batteries. I replaced them with Iris Contacts and never had any more issues.
I am up there in devices as well. I feel your pain.