Hiring a catcher is different from starting the exploration. When you hire a catcher (say, you want three Mammel catchers), you pay for the catchers. When you start an expidition, you're paying for the expidition itself.
Hiring a catcher gives you more of that type of catcher.
Starting an expidition carries a seperate fee.
Does this make sense?
Edit: Essentially what you're doing is paying for the number of catchers you want. You then pay them to go on the expiditions you choose.
"You know what the issue is with this world? Everyone wants a magical solution for their problem, and everyone refuses to believe in magic."
- Jefferson/The Mad Hatter, Once Upon a Time