What are you talking about? It’s not all dollar cost. You can’t eat what a solar farm produces. A solar farm does not replaced the carbon sequestration of a forest. Endangered species displaced by solar farms (desert tortoises, for example), do not benefit from the “value” produced by a solar farm, quite the opposite! This is what the “nuke bros” are talking about!
We can assign monetary value to things and then compare them. Food, for example, has value mostly because of enjoyment, not because we absolutely have to eat (the elasticity of demand for beef is an example of this.) The value of the ecosystems displaced by farming, PV, or other land using activities can also be assigned a monetary value (since it's clearly seen as tradeable against economic benefits.)
Given that, we can ask what's the ratio of the value of the output of a farm to the value of the displaced natural ecosystem, and do the same for PV. And if we do that, we will find the ratio is MUCH higher for PV than it is for farming.
So, if the goal is to maximize utility for a given displacement of natural ecosystems, we come out ahead (on the margin) if we use land for PV instead of farming. If we want to return land to nature at lowest cost we would do that by returning farmland to nature, not PV land.
