Gallium is not cheap at scale. We can only produce trivial amounts, and it is cheap because we don't have many uses for what we produce. It does not form concentrated ores which means it cannot be mined in any conventional sense.

We extract it from aluminum (and zinc) refinery waste because it is relatively convenient in an industrial process sense, but the amount that can be produced this way is inconsequential. The gallium in all the known aluminum ore reserves is measured in kilotons. For this application, we would need something closer to gigatons. We could produce the necessary quantities if that was the sole objective, but the cost per gram would be closer to gold which is not great when you need gigatons.