Dumpvalve...I doubt very much that this is a major issue. As most of the Cabin Crew as well as the Flight Deck Crew will confirm, a no-alcohol policy during flights will avoid hundreds of incidents we are facing every year.
A "sober" flight will not lead to any discomfort and I am pretty sure that a lot of passengers will welcome such an environment.
On the other hand...if the passengers are prepared to pay the price, I am sure they will be able to get what they want....