Acoustic treatment question: do you agree with Dennis Foley that $46k to $65k is required?

That price for activated carbon above is totally out to lunch. Activated carbon starts at about $0.5/kg.  Let's they need a specialty grade so 10x maybe. They aren't buying it on Amazon.  Only highly refined scientific grades would be the cost quoted above.

I think I sent you some links on Foley. You have your answer. He does not have a lot of respect in the industry.

I am new to shopping for acoustic treatments. I thought that Foley’s company was a competitor to GIK, ATS, etc. (which are "generic" products, in your terms). But now I understand Foley aims at a clientele that wants to pay his prices for his solutions. I misread the intent in his video, which I thought was aimed at a wider audience. I appreciate your comments. Thank you.

His target market is people willing to pay the prices he charges, not people who need to pay the prices he charges.  Most people's acoustics are poor enough that almost anything is an improvement and will elicit a positive response.

Without a purpose-built listening room it's unlikely most homes have a floating room with very good ratios and built with multi-layer, heavy, damped construction. My current listening room has those qualities and it still required 32 tuned Helmholtz resonators in the corners, broadband membrane traps against the front wall, RPG Diffractal arrays across most of the back wall, and 4" 703 clouds over about 80% of the ceiling and 70% of the side walls. That treatment takes into consideration that the low frequency modes will already be well spaced and the treatment only enhances what is already a very even room.

What is required in a recording studio though is different from a listening room.  A listening room has the benefit of fixed speaker position and listener.

In a listening room as well, and as it suits personal preference, some reflections are a good thing to enhance sense of space that is often preferred over what can be a flat presentation from the recording. To that end, I would expect most people would not find ideal to have 70% of their side walls covered with thick absorption and probably not 80% of the ceiling, though you have not described the floors.  Covering that much ceiling but leaving the floors "live" can create an unnatural presentation depending on the speakers.

Your implementation of the 32 Helmholtz resonators really speaks to the alternate implementation of a bass array for controlling the lowest nodes. For most users and their rooms, when cost, looks, space, etc. is taken into account, a bass array will be a better, more cost effective implementation. 

16.5 lbs/sq. feet, yes they are heavy. Look really peaky though. Lots of absorption at 50Hz, lots at 250Hz. Not a lot anywhere else.  Better hope you nodes are there or you may not get what you want:

https://acousticfields.com/wp-content/uploads/2012/01/ACDA-12.pdf