Yikes, if its anything like the boutique preamps that Danny “Sage” Mckinney sells on his WEB site http://www.requisiteaudio.com its about $4-10k worth of hushed secrets and mumbo jumbo! The man sells 8ft of XLR for $400 and an amorphous "upgrade to premium components" for +$2600 on a dual mic pre. His remakes of Standel amps are more conventional looking, though not cheap at $3500 for a combo.
From the way Ry speaks about his Green Man it sounds more like an attenuating filter than a boosting preamp but the praise Ry throws at the preamp means its going to be a closely guarded design and probably never made affordably. Good luck sussing it out!