I think it's $39 for a 2 hour session which is more than enough. You need to make a reservation if you buy a day ticket. They have a 6 pack that costs $199 that goes on sale from time to time for $99. I buy the sale 6 pack which doesn't require a reservation.
I don't know if they cap ticket sales. We usually go midweek at 1pm when they open so not crowded at all.
Apparently winter is their busy time not summer which surprised me.