ExXB - 03/08/16 you said:
"... And the price of a 330 ml tin of beer onboard? £4! That's £6.88 a pint. (4/330*568.2612) and applies regardless if the airline has paid excise taxes or VAT.
No wonder people buy the 'cheaper' airport beers, or drink their duty free.
Sobering ..."
Again, the airlines don't charge the prices and are not responsible for the VAT or excise duty, it's the catering companies, a fact that you continually ignore to your convenience.
I don't think bars should be closed. In fact they should be open at any time the airport is open. However some responsibility must be taken by the airports. If you've done worked for the airlines you'll know the point of an airport is to squeeze as much money out of the punters as possible, then get them onboard shut the doors and let someone else take care of the problem.
Look at most Uk airports where miniatures are placed on podiums through the main walkway. They are inescapable and are clearly there to promote people to buy and drink onboard. He ground staff are also very careful as to their wording for example: "you can take the drinks onboard", conveniently missing the important part which is that you can't drink them onboard.