Performance expensive mesh trick, what can I replace it with?

Hello, I am trying to make some planets for testing, the models have sphere meshes stacked on top of each other so it looks like it’s 3D.


However, it’s far from having no impact on performance, because I have to set it’s transparency to 0.02, so it’s more visually pleasant from up close.
I need ideas on what to replace this “mesh trick” while still maintaining the same 3D effect.

Without transparency on Quality Level 16 (Little to no impact on performance when close, but visually unpleasant, aproximately 7 fps loss)


With transparency on Quality Level 16 (Huge impact on performance when close, way more visually pleasant, almost 40 fps loss)

A 3D model of the extrusion instead is the obvious answer.