You and I are in agreement. Christmas tree lights don’t use these expensive devises. The true blue LED is a Noble worthy achievement
7¢ each in 5000 quantity for a name brand at Digikey. If you are making Christmas lights you will get a lot more than 5000 at a time and go for lower quality (different brightnesses or dominant wavelengths) to get even cheaper. The days of $1 blue LEDs are past.