I'd bill 20% minimum.
I re watched the original video.
I had completely missed the fact that the manufacturer seems to have sent the amplifier to Mark themselves with that challenge!

I hope he sent it back properly packed...
...perhaps filling it with builders expanding foam to make it more rigid before giving it to the Evri van driver.
X
I though it was a customer, after the manufacturer refused to repair it.
I watched the video, and the construction was obviously a joke, that "shielding" is made by someone who ahs no deeper understanding of electrical fields. If you want to shield it you build it in a mu metal enclosure for starters, or at least Aluminium, not laser cut acrylic.
The standoffs seems to be identical that you get from Aliexpress in a kit for 1.99 including shipping.
I honestly don't know why anyone would want to own this preamp. Even before it was opened and reviewed. There is one reason, and that's consultants building a system for you, and getting paid percentage, based on how much they spend on it.