Question about XM-L tints and bins

I was recently looking on Digikey at some XM-L bare emitters. The cool tint is offered up to T6, neutral up to T5, and warm up to T3.

- Why are lower color temps only available in lower brightnesses/efficiencies? Is it simply Digikey's offering, or does it have to do with LED chemistry?

Also, the highest binned LEDs are around $11 a piece, where the next step down (eg. T5 vs T4) is like $8 something. I assume this is because people will want the brightest possible light so they can charge more, but...

-Is there really any noticeable difference between two adjacent brightness bins? I understand our light perception is not linear, so it doesn't really make sense to spend 30% more for neglegible light increase (~60lm @ 3A), does it?

Brighter bins have lower yields, which is why they cost more. Warmer color temperatures have lower brightess due to the thickness/density of the phosphor applied to generate that color temperature.

If you want to know more about these LEDs, the Cree provided datasheets are a great place to look.

Shamelessly copyrighted from Selfbuilt's tint comparison... Hope this explains it, most modern LEDs emitt blue light, which hits the yellow coloured phosphor coating on the substrate, which emitts white light in return. As you can see, the warm white emitter has a thicker layer of phosphor (appears more orange) and therefore emitts less light overall.