I won't be willing to pay more than I pay today. If prices go up noticeably, I will either (a) go less frequently, probably be reducing the number of times I see shows multiple times, or being that much more selective with my purchases, e.g., I didn't really expect to like Spiderman, Gary, Addams Family, etc., but I went anyway (and disliked them even more than I expected); or (b) buy worse seats than I have gotten for the past 4 decades (for 10 - 15 years, I always sat in the rear mezzanine or second balcony...I can do that again, if I have to).
Bottom line: I am not prepared to spend a higher percentage of my disposable income on theatre, at the expense of something else, just because ticket prices go up a lot. As much as I love theatre, by the time things open up, seieing half as many shows as I have historically seen will still be significant by comparison.