The revenue premium collected is not for the DBJ or hat. It is for the DL package, as mentioned above. I'll suggest it's due to the on-time performance, irop recovery (which the customer just sees as DL's "plan B" when things go bad), free bag, decent check-in experience, bording, in-flight comfort and amenities. We also get more for the origination/destination pairings and frequency of flights. These are the things customers are willing to pay a bit more for. Not the pilot costume. It helps convey the image, and the marketing of the brand, but no one has ever said, "I'll pay more to see that DBJ and hat". Instead, they'll pay more to get from "A to B" in reasonable comfort and the least amount of hassle.

The most likely thing a pilot can wear that will impress a customer is a smile. Everyone's got one and it doesn't cost a thing.