I think Breibart exaggerated the longshromen's pay more than slightly.
According to PMA's website (the company in the OP):
The analyst firm has compared salary data from Pacific Maritime Association’s (PMA) homepage with the average salary in the U.S. According to the website, the longshoremen on the U.S. West Coast earn an average of 98,603 USD a year including two and a half weeks of vacation on average. The earnings are about six times as much as the minimum wage in California and more than double the 42,000 USD including bonuses, which is the average salary for all Americans, according to Silicon Valley Index
U.S. longshoremen earn three times average national wage
This analysis was published on July,13, 2013.
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This works out to roughly $380 a day, less than 1/3 of the $1200 per day Breitbart reported. Now they could have had a pay raise, but it's very highly doubtful the longshoremen received that large of a raise in a year and a half.
Why anybody takes Breibart seriously baffles the mind. They seem to be constantly full of shit. But the loyal goose-steppers keep coming back for more complete bullshit.
However, $380 a day is still pretty outrageous. It's more than two times the average wage earner makes.