Yes, having no paint saves weight, and yes that saves money, but it's not that simple. Paint may weigh something, but it also does a very nice job of preventing corrosion and protecting the skin in general. When an airline like American goes with bare metal, it has to do some additional work to make sure those skins stay in great shape.
Every time I've seen this question raised, it was generally thought that the difference in cost was nil. So, I rolled my eyes when someone brought this very question up at NBTA in July, but then I started thinking about it. And I think Delta CEO Richard Anderson and Air Canada CEO Montie Brewer both started thinking about it as well.
Air Canada has even gone so far as to strip the paint off a plane to test it out, and they found that it wasn't going to save them much if anything. But then up on the stage it was like a light bulb went off. Fuel is a lot more expensive now, so the savings may be greater looking at the current price of fuel. Very interesting.
Both CEOs said they'd be looking at it again, so I wonder if we'll see some more airlines start trying this out now that there are greater fuel cost savings to be had.