Sounds like you think into it waaayy too much. First off there are many bars that do not have beers/drinks at an even price…and they do just fine. It is done many of other places and it is not a problem.
Fact is it is very simple…people will be pissed and a few people won’t go to the bar for a little while. This will only last for a short period of time. People like going to the bar too much…to meet up w/friends, get away from the bitching wife, pick up chicks/bar sluts/dudes…and they will go back to the bar and the extra $2 they spend will not really make a difference. This is sort of like the smoking ban…sure the pussies will bitch and moan…but in the end people will still go to the bar.