alt Hacker NewsPaint has been well studied. We know how to do it really cheap and automated these days. Cheap is relative. I'm sure that we're talking tens of millions of dollars to get all the equipment needed. But on a scale of factory and for how long it will last, that's cheap.
Flat metal is more expensive than curved metal. Curved metal, you design the curves to help support the stress points: you can get by with thinner sheets. Flat metal requires thicker heavier more expensive sheets of sheet metal in order to be strong enough.
Curved metal also lets you design the whole thing to be more aerodynamic. which is an important consideration even with something as un-aerodynamic as a truck.
> I'm sure that we're talking tens of millions of dollars to get all the equipment needed.
Painting cars really is a hugely optimised process that materially affects performance characteristics such as weight.
Its very difficult to appreciate just how many cars are made worldwide wide, but just think if a completely optimised fully robot optimised line cost a billion dollars, in only needs to process a few million cars to fully pay itself off. Just look at how much a “paint option” costs. Enough people paying for a premium colour would completely pay for the entire production painting line.