It is very obvious that using a helicopter to return back is an expensive add-on over the regular trek price. The cost also depends on the number of persons sharing a helicopter while returning. Generally, from Gorak Shep a helicopter is permitted to carry only 3 persons owing to the thin air in the atmosphere. The costs also varies depending whether you wish to fly back to Kathmandu or just up to Lukla and then continue with the regular flight onwards.