It's a fact that a lot of folks don't appreciate, but the biggest single expense in running the average zoo is the staff - up to 60% of the operating budget at many zoos is staff salaries. Very often, it's keeper time and staffing levels, rather than physical space or cost of animal care, which limits a zoo's ability to house as many animals as you might otherwise suspect they could hold. What I'm getting at is, having a keeper stationed all day at a croc walk-through might not be the most cost-effective choice you could make for a zoo