They also require somewhat obscure rare-earth elements, which are not getting cheaper. https://en.wikipedia.org/wiki/Phosphor https://en.wikipedia.org/wiki/Pho

They also require somewhat obscure rare-earth elements, which are not getting cheaper. https://en.wikipedia.org/wiki/Phosphor https://en.wikipedia.org/wiki/Phosphor You'd also have to scale strontium mining and refining back up.