See, my thinking on it is this - if the Nix folded tomorrow, would those 10 or so home games a year be replaced by 10 other events hiring out the stadium? Clearly the answer is no, so it's in the interests of stadium management to do what they can to keep the nix in business too. If the prices really are high enough to drive the Nix away or make the club unsustainable then ultimately that means less money for the stadium in the long run. So both parties have a vested interest in finding a price that doesn't cripple the club. Hopefully they see it that way too.
In other words, that stadium might have a monopoly but they have a very small market so pricing even one client out of that market could have serious impacts on their bottom line.