[goda90]

Are LED's particularly costly though? Does one wavelength of red LED differ significantly in price from another wavelength of red LED? And does that even matter that much? It seems like higher wavelength has deeper penetration, but how deep you want depends on use case.

[literalAardvark]

You would get deeper penetration from very high power leds driven intermittently though.

So there may be a very different grade of led in the pricy stuff.