Max Payload Question

I've noticed that there is a huge gap between the max payload shown on the brochure and the door sticker. Does anyone know why there is about 300 lbs difference between two?

 

The brochure shows the payload for the base model. The combined weight of the items you have highlighted is 300lb and is a constant static load, added to your truck reducing your payload by this amount.

 

That's what I thought initially but then I realized that all three items are standard on the limited or above. It seems like the max payload shown on the brochure is misleading and impossible to achieve.

 

I’m in agreement that the way this is presented seems misleading and a bit obscure.
I wonder if the “big 3” do this also when they rate their trucks.
The primary motivation behind this, I believe, is the extreme measures every manufacturer is taking in the design to cut weight and thus improve the mileage and weight/power ratio.