[tim333]

The "local guides" work kind of splits into two parts. The vast majority of the work the Sherpas and Tibetans do is logistics, lugging tents, ropes, food and the like up to the various camps, and no one uses oxygen for that. Oxygen is pretty expensive, like $400 for a cylinder that lasts a few hours. The last bit guiding up to the summit, the guides are often westerners but even when they are locals they usually use oxygen for the summit. I had a go climbing and when you turn off the oxygen you don't collapse or anything but you can climb like 3x faster with it on, and you get a gradual body deterioration with it off, at the high altitudes - I got to 7900m.