I'm guessing that question wasn't "politically correct" or I shouldnt have asked.
There's nothing wrong with the question, there just isn't a good answer for it. It appears like you have a monopoly on karaoke in your area. This doesn't mean that you should take advantage of the situation by overcharging but if it is obvious to you that you are generating large profits for a place, that is not fairly compensating you, then you should renegotiate.
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