Conrad, no one is arguing for exclusivity or high prices. However there is simply no evidence to support your claim that high beer prices are an obstacle. Folk music is still one of the cheapest forms of entertainment around, and most people can go to a music event and have a few drinks for far less than it would cost them to go to other forms of entertainment. If they are on a tight budget, they can drink less - the only reason that you find prices an obstacle is your refusal to do this.

In my experience, as a performer and an event organiser, the main factors contributing to a successful folk venue are these (in descending order):

the quality of the music - this is paramount, a perfect venue is no good without good music.
the right location
a suitable room:
- the optimum size for the size of audience (too big can be as bad as too small)
- the right shape, so everyone can see
- good acoustics, so everyone can hear
- ideally, separate from the bar itself, to keep noise down
the right atmosphere
the quality of the beer
the price of the beer

Obviously, if all the other requirements can be satisfied then cheap beer is to be preferred over expensive beer. However in terms of what makes a good folk venue it is of only minor importance compared with the others. Choosing a venue based solely on the price of beer will deter more people than it attracts.

I have not mentioned food, because this is not a consideration here. People don't go to folk venues to eat. Perhaps it's different in the US.