Costs of installation only go up? There has been steady improvement there, particularly at utility scale. No more expensive poured concrete foundations, just screw earth anchors into the ground.

Or are you talking labor-intensive installation onto residential rooftops? Well, stop doing that, it's kind of stupid.

Real estate costs are a tiny fraction of the cost of installed solar in much of the US, and in much of the world. A solar powered global economy will not be putting many panels on the small fraction of the world's surface that's unusually expensive, but will focus those panels on places where it's cheaper. It's the same reason we don't grow wheat in Manhattan.