These are typically representative of cost performance per watt of one part of a more complex deployed energy system. Things like the aluminum / steal for the container / framing, copper / aluminum for the transmission and wiring, land and labor for installation decline at much less aggressive rates or increase over time.

In almost all pareto optimal least cost energy system models that I've seen, high penetration of solar, wind, batteries plus some minority amount of (clean) baseload power is the most capital efficient energy system.