I don't know the reason for the lack of 420nm either but it probably has something to do with it being on the periphery of what we as humans, the ones actually buying the product, can see so it makes for less overall brightness in the tank which is something LED's already seem to be at a disadvantage as compared to other forms of reef lighting like MH's or CFL's. Also people love to use PAR meters as a metric to compare the output and with the most commonly used PAR meters out there under-reporting the PAR values from blue LED as it is already adding even bluer ones will probably drop the numbers a fair amount more as well. Sure they could add more overall but then the power budget goes up and a bigger driver and fixture will result and the price is only going to get more expensive, something you and others already seem to balk at which is entirely your prerogative.
The bottom line is they have to sell the product to be able to make it better in the future so they probably went with a final configuration which covered as many bases as possible i.e. looks good to the eye, can grow most things, is of reasonable enough price compared to the competition to sell well etc. As LED's improve they tend to get more efficient, some just get more efficient at a given monetary cost but some get more efficient at a given power budget too, so it is entirely possible new LED "packages" could become available that have more spectrums and increases luminance and PAR all while using the same 130 or so Watts.
ETA: just curious why if you think the $750 is out of order why you would care enough to post about the Radion to begin with? If you think they are overpriced and don't deliver what you consider a critical part of the spectrum why would you even try to acquire them to begin with?
First off, Ecotech has an extra channel to already use so the driver won't get any bigger. Will they use more power with more LEDs? Yes, they will but they can pull a couple of the blue LEDs to compensate for this. Why use Royal Blue and Blue? They have almost identical spectral graphs with each LED just barely peaking at a different wavelength. Pull 1-2 of each and the 420nm LED will fill in the gap.
You are right that 420nm light isn't that bright to the human eye but that hasn't stopped people using actinic bulbs for decades, has it? Just because humans can't see violet light all that well doesn't mean that corals can't see it. In the end we are keeping CORALS and not humans in our tanks. So what if WE can't see it all that well. If the corals can and it is an important spectrum for them, we should provide it.
Why would I post about the Radion? I think $300k is out of line for a Ferrari too, but that doesn't stop me from having an OPINION about the car. Why would I try to acquire a Radion? It is super easy to slap on (2) 403nm UV Stunners from Ecoxotic and cover the lower part of the spectrum. Will I see the difference? Nope, I won't. The 403nm stunners are dim to our eyes like we already pointed out but the corals will see it.
Actually, even though the violet wavelengths are dim to our eye they provide pretty good PAR. You just have to use the proper meter to read them. I will try to dig up the link of a company that tested the PAR on some UV LEDs and the numbers were pretty good actually. Just because Apogee PAR meters have a serious disadvantage at reading lower wavelengths doesn't mean we should just say "F" it and not provide what is NEEDED for corals.
How do we know that the Cholophyll A spike at 417nm and the Violaxanthin spike at 425nm isn't responsible for certain colors? I have never once seen a study where we, as humans, actually knew where all the different colors come from and how to get those colors out of our corals.
Yes, I understand that the blue LEDs slightly touch on the 420nm area but it is a VERY small amount and nothing goes below that. All I am saying is adding a couple 420nm LEDs isn't going to hurt anything and if done right, shouldn't cost too much more either. If you are going to spend $750 on a light, you will spend the $775 if they bump it up. If you are going to tout being a FULL spectrum light, provide light within that FULL spectrum. T5s and MH can say they are FULL spectrum because they have light all throughout the 400-700nm range and even have UV and IR light. We use shields to filter out the UV and that is a good thing so we don't need LEDs that provide actual UV. Infared light is not used by corals either (to my knowledge) and is mostly used to heat the water. Therefore, we don't need any IR LEDs either.
Again, I am NOT bashing Ecotech. If Ecotech or anyone else wants to think I am, I am truly sorry you feel that way. I have never once said the Radion sucked, or that it is a $750 "softies" light. I don't even care if the PAR is lower than the competition because I understand that PAR is really pointless in the end. PAR is a good baseline but nothing more. It isn't a holy grail or magic formula for success.
The Radion was a giant leap for us here in America. We were stuck with AI, Marineland and Chinese LEDs for a long time. The Radion changed the game and I still think it is a great fixture but there are areas for improvement IN MY OPINION. I hope that Ecotech (and others) can see it that way. Other LED companies already allow the option for 400-420nm LEDs and so should "America's Premier LED Aquarium System."
That is all.
Again I didn't really see you attacking Ecotech without basis, just wondering why you cared if you don't have a dog in this fight. Also I hope you didn't see my post as an attack on you. I just think you look at the technical side a little too much and lose sight that there are market forces at work that force compromises. I want a nice light but I also don't want to be the only one who has it and a company that produced it out of business either 
