|It seems to be playing to about 95 percent of its theater's capacity, week after week. You have to remember that its theater, the Booth, is one of the smallest on Broadway--773 seats. If the show were playing to capacity at $100 a ticket (slightly, but only slightly, above last week's average ticket price), it would still only be grossing $624,000 a week. $600K at the Booth isn't quite the same thing as $600K at the Winter Garden.
No, the show isn't a box-office blockbuster, but I imagine its grosses are within the range that the producers were anticipating.