The official route of the Pan-American Highway through Mexico (where it is known as the Inter-American Highway) starts at Nuevo Laredo, Tamaulipas (opposite Laredo, Texas) and goes south to Mexico City along Mexican Federal Highway 85.
Individual, Family, Dual Premium, and Family Premium Members receive a discount on tickets to the 4-D Theaters at Central Park Zoo ($4 Member/$7 non-Member) and the New York Aquarium ($3 Member/$6 non-Member). Conservation-level Members have free access to these attractions.
Let's take this number, and divide it amongst the 11 Parks world wide, and you get $92,363,636 per park per year. Of course the Parks are open 365 day a year, and that comes to approximately $253,051 per day. Now, keep in mind, not all of the Parks are of the same size, and some Parks need more staff or services than others. But, if all you are looking for is rough estimate ...