25b: origin of discount rates

MM comments that discount rates “r” are asset-specific, not investor-specific. Why did he say that?

I thought the whole point of discount rates is that individual investment firms make a decision on their required rates of return before making a play.

If this discount rates are decided by the asset, who decides that for everyone and what is their methodology?

Inasmuch as I’m not skilled in abnormal psychology, I cannot say.