Unless it was a first time for an event, and even with all the planning in the world, the event was overwhelmed the first round, then charging 25% -50% doesn't seem appropriate. If you want to eliminate the snoot factor, explain in your advertising the rationale for the large increase, otherwise you run the risk of alienating people.
I have to say that I am surprised that the Johnny Cash show sold out. The price without serving food of some sort seemed extremely high, even in light of the amount of bands attending. My first thought was how many people could sit that long waiting for ALL those bands to finish singing A song and did one want to hear bands of different genres sing music that may not suit their voices. IMHO, The sell out probably has more to do with the amount of bands playing and their friends and families attending, as well as frequent Rep contributors, than it had to do with the value of hearing Johnny cash songs by artists that you can see frequently for free around the area while enjoying a meal or drinking at a bar.
There may be many events that are free admission, but, let's not kid ourselves, people who attend spend money in some shape or form at them which is good business practice.