It was a lot of money for such an easy job. He did not expect to get that much money. This is very informal English. You might also hear "crazy high" or "ridiculously high". Good luck with your studies Shahbaz!

In this instance it means overpaid, which is to say, the job that was done was too easy and it was overpaid for. I hope this helps. If you need a tutor to help you advance and improve your English I am available for that, you can check out my teacher profile and book a lesson. Cheers