So, just to be clear, they call out F-150s over $50k, not all F-series.
That's right about the dividing line between work truck and luxury truck. <$50k buys a SuperCrew XLT 4x4 with the max tow package. Basically, it's the best "work truck" F-150 you can get.
Everything beyond that are luxury trim packages. Heck, you can't even get a 8' bed unless you go for the lower tier trims. Which points to the XL/XLTs being the work trims and the Platinum/Raptor/Tremor/King Ranch being luxury trims.