Out of 16, or 17 elk that I have killed over the years, I have never been close enough to use a vehicle for any of them. I have always used the Cabela's Outfitter pack for my off-road deer, antelope and elk hunts. The heaviest load that I ever had in one, was 110 pounds. I retired one years ago, that I figured had hauled out 1500 pounds of meat, or so. It now supports a backpack sprayer.
I did haul a couple out on a plastic sled, which is definitely the way to go, if there is enough snow to support it. I have kicked it loose on steep slopes and restarted my hike 200 yards later.
I always bone out the meat and leave the heavy bones in the hills for the critters. Never saw the reason to haul out something that I was going to throw away when I got home, anyway.
I am pretty much done with the hunting in treacherous country, as I get clumsier every year. There have been a couple hunts/pack-outs over the years, where I have questioned my sanity, for being there alone and in grizz country to boot!