Metal cabinet speakers

I think a lot of companies have dabbled in metal cabinets but most don't stick with it.  Infinity did it with the intermezzo line and the Prelude MTS.  Thiel had a number of models - powerpoint 1.2, viewpoint.  ATC had a metal line for a while.  B&W had some metal boxes.  My Thiel 3.7s have aluminum baffles and an aluminum top.  

I'd guess it doesn't provide enough performance improvement to justify the cost.  There are probably other areas where the money spent on metal cabinets can provide more performance.  The companies that moved away from it are capable of doing a lot of different things, have tried various materials, manufacturing techniques.  I'd guess it's more of a sales feature in cases where companies are making entire big square boxes out of aluminum.  Something to talk about that differentiates them from other brands.  

How about concrete?  You can get the stuff they make concrete countertops out of at a store near me for around $15/bag.  Past a point it seems it would make more sense to have portable forms and pour the box onsite.  Or have the box made out of interlocking vertical layers that stacked on top of one another.  How inert and resonance free would a box be if it were brick and you just had a brick layer lay it in your listening room?  It wouldn't cost much.  Maybe have a light box and cover it in a thick layer of concrete.  If performance were really the point of these ridiculous boxes there are bound to be a lot of better ways to going about building an inert box than spending 120 hours machining aluminum.  

The thing is, past a point it can't possibly make sense to have the entire speaker delivered to a house.  You can do a lot of things for 100k, let alone 500k, that you can't for 10k.  It's a very different situation and calls for a different approach.  Or it would, if performance were the primary consideration.

The entire box doesn't need to be made out of concrete.  You could make the baffle from aluminum or some other material that is practical.  My point is that making the entire box of a ludicrously expensive speaker out of a single material is ridiculous.  Making it in a factory and shipping it somewhere is ridiculous.  It doesn't translate if the point is to get the best performance for your $685k.  What is going on here is that the guys who make the decisions for these companies have been around enough rich people to know just how vulnerable their vanity makes them.