It's the same reason a Captain has an FO. Occasionally, even the best of us make mistakes, and we can be completely blind to it. Having someone else checking can save your life... or your career. If that's not intuitively obvious, FedEx might not be your best fit.

I’m not saying don’t have someone look over your app but what advantage does paying someone $300 give you to do it up over anyone else?

Many apps are screened and picked by a computer. People who specialize in this stuff can spot things that may flag a computer but not the human eye. They are also useful in tailoring your app to what a specific airline is looking for.

Then don't. Your money, your decision.

No they can’t. They are selling you a product and have convinced you that they can do something special so that you give them $300. Conveniently the whole system is not transparent so you have no way to verify if they actually helped you or not.

Cool, good luck with that!

That’s what I used to always say to the guys I flew with at the regionals that refused to pay for app reviews, job fairs, resume development, etc. I happily encouraged them, as it was less competition for me.

Many of them are still there, quite senior CAs still trying to move on. Meanwhile, I’m making more than twice as much and work half as hard. Well worth a bit of investment!