You are right that they may not be that cheap, since hitting the right wavelength is the issue with standard LEDs/plus lumens.

I take it this is the product Procyon 100 [Procyon 100] - $600.00 : Buy LED Grow Lights, Procyon 100

It seems to use smt leds it seems.
56 CREE* Xlamp high power LEDs (40 635nm, 16 470nm)

I'll try to resource this a bit more.

Cree reports lab development of 86-lumen LEDs - compoundsemiconductor.net
Two years old news report.
"indicates that the LED industry is at least two years closer than previously predicted to achieving the "holy grail" of 150 lumens per watt." If that's true that's pretty much as good as HPS of course wavelengths will become an important factor, but hopefully its not too far into the future.

If you guys dont want me spamming LED info just let me know. :jointsmile: