You should get a better return at a charity auction if your clients are any good. I have often seen 100.00 bottles going for up to 500.00.
The idea is to get whisky drinkers at tables to purchase it as a group and they can then drink it amonst themselves at the event.
If you are in the UK a measure is 25mls so that equates to 28 measures but you can round it down to 25 measures if you like for spillage

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How you whipp up the crowd is by saying stuff like 'who would can't pay £5 a shot for a 36yo whiskey(which by the way is very resaonable) come on now start me off at 140.00 okay lets say 100 that's only 3.50 a shot' .... and you can pre work out the price per shot up and up and groups may be happy to pay £10 a shot which equates to 250-280.
Or simply sell of the bottle in measures for a tenner each and saves milking the crowd. I can't see why you would not sell 25-28 measures at a charity ball.