Why do the FBI agents get paid so much money?

Because they work so hard:)

Added:

FBI Special Agents are on call 24 hours a day 7 days a week 365 days a year, just like most other Special Agents. They work when you are a sleep, on Holiday's, rain or shine. $56K to start is not a lot of money in New York, DC, LA, or Miami. They work hard and we are grateful for their efforts.