Solar historically declines in cost by 24% for each cumulative doubling of production (of the solar hardware). Solar is about 4% of global electricity production now, so scaling it to saturation (just for current electricity demand, which will grow as the world becomes richer and more electrification replaces fossil heat) would drop the cost by another factor of 3.
This only worked while panels were the lion's share of the cost of a solar installation. These days, costs of real estate, installation and grid connection far exceed the cost of panels -- and those costs go up every year with labour costs rather than coming down.
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.
This is all just delaying the crossing point though. Nuclear fans are betting nuclear's costs fall while renewables and storage run into brick walls and stop getting cheaper. It's not clear why one should assume this, or why an investor should bet on that outcome. And it is just a financial bet; in the worst case for renewables they just come in a bit more expensive than nuclear, so it's not like the economy explodes.