It was in the 1990s that more amateur climbers began to attempt scaling some of the world's most difficult peaks.

Tibet has five peaks that are above 8,000 meters, more than 70 above 7,000 meters and thousands above 6,000 meters. Tibet's three 8,000-meter peaks - Qomolangma, Shisha Pangma and Cho Oyu - see more than 1,000 mountaineers annually, according to the Tibet Mountaineering Association.

It can cost a 10-person expedition team up to 2 million yuan ($307,700) to make it to Qomolangma's top, Nima Tsering, principal of the Tibetan Mountaineering School, says. This includes the hiring of guides and other support services. By contrast, in Europe and the United States, one climber can be charged around 50,000 euro ($76,900) by companies offering mountaineering services, he says.