As for cost, as a Board Machined for a TT Chassis my last purchase worked out, (inclusive of Cutting Up the full size board by a professional cutting service) to £100 per Board Cut at 500mm x 400mm x 25mm delivered to the Door. I was gifted a CNC Cut Out, for the Chassis, but this can be achieved in a variety of ways, if one has the confidence in their skills and correct tools.
Granite in the Past has far exceeded this cost when produced as a Laminated Tiered Structure with a Tidying up to the aesthetic. The owned Slate as the Raw Material with a Highly Polished Fascia, as a salvaged/repurposed item, cost some time ago approx’ £70 for a piece large enough to do Two Plinths as a Single Layer or one as a Laminated Two Tier Structure. Add the Cutting and aesthetic work to this to tidy it up and the cost will exceed the cost of a P'holz Plinth.
These Stone Materials are no longer wanted, they are definitely Superseded as a Plinth Material. There is real benefit in not having to arrange for a Logistics Plan to move them, I am still experiencing this with Corian and it is not healthy on a Getting Old Bones Body. P'holz is a much friendlier material for such purposes.
Where P’holz has a further advantage is that a Thickness of only 10mm produces all the desirable measurements referred to in earlier made references.
Adding Tiers or using a Thicker Board does not show any alterations to the Measurements that suggest there is a further improvement to the Damping and Frequency Data recorded.
As said in a previous post, I know one individual who produced a P’holz Composite Plinth, which was designed to have a much increased Mass using a material that has proven through measurement Damping Properties. This Plinth when produced was in use as the main Plinth. After a period of time and when eventually having produced a P’holz Only Plinth. The comparison took place of the Two Plinths with the same Modified DD TT>Tonearm>Cart’ and Support Structure.
The Composite was proved to be not as attractive to their preferences and returned to a Naked P’holz design.
This individual now has Two different versions of Modifications carried out on the same Model DD TT, which are both mounted in P’holz Plinths. The idea was to keep one TT as original, but the TT in original was not tolerated any longer after experiences the impression made from the first modification.