There's big money in shipping items across the country or globe. People know it's not cheap, so they're willing to spend a lot of money to get their items where they need to go. Not to mention companies whose whole business is the shipping of their goods to different places. It's not surprise that the job of cargo loader, although not prestigious, would pay a lot. There's vast amounts of money at stake every day as items are shipped. One missed shipment could mean incalculable costs now and into the future. Cargo loaders are trusted, and paid for, that responsibility.
A cargo loader can make anywhere between seventy thousand dollars a year to five hundred thousand dollars a year for a foreman. You're probably looking at more around seventy thousand dollars to one-hundred and fifty thousand dollars, but that's still very good.