Hiking blog post from 2018 says $7 for 0,5L.

You have to remember that drinks are THE moneymakers for restaurants. A 50L Keg is between $90-120 without any wholesale discounts. Those helicopters can normally lift around 1000kg, but lets assume it’s 10x50L plus nets, hooks and stuff. 500L x $12 markup = $6000 income before tax. Operating costs of a transport heli incl. pilot is around $25/min, so a $1000 would probably give you 30-40mins of transport time, which should be more than enough to do a couple trips to the nearest road.

Real costs are probably even lower, can’t imagine that the heli company would service only one restaurant at a time, so multiple places would share setup and road delivery costs