If the advance is $28M for a 15 week engagement, then that's roughly $1.86 million per week, which is great for a play! I'd say the grosses will be fine as long as the 2 stars above-the-title don't have significant absences that entitles the patrons for a refund.
Yes it seems like the only affordable way to see the show is via the lottery. However, if the show gets mixed-negative reviews or word-of-mouth, I can see the secondary market prices decrease to more affordable prices.