FWIW, I'd assume that any recorder not made out of wood or plastic would be more expensive and not less. Different construction techniques needed and all that. The mention I saw regarding carbon fiber recorders was that the wood ones were superior, too.
I don't know anything about recorders other than my kids plastic school recorders, and a desire I have to make a few wood ones on my way to see if I can recreate some clarinet joints.
carbon fiber recorder. Interesting.
I'd be worried after some time of wear of the epoxy on finger holes exposing the fibers which can then easily penetrate the skin.
I'm sure anyone can make one of any material that you want.
I've been wanting to make some alto recorders as experiments (someone on this board posted an example of this).
But once you can make on our of one material it's just a matter of the correct tooling for other materials.
Aluminum & brass blocks would require much stronger and sharper tools than used for wood. Also a more durable metal lathe.
I don't see anything impossible about it.
It's just the market for making those.
I don't think it's "if" someone can make an aluminum or brass recorder, but "who would buy" an aluminum or brass recorder.
If there was a market I'm sure someone would make a solid silver or gold recorder too. But that requires an investment in tooling to get there, thus the "custom" price would be there like flutes but probably much more as there may not be many buyers.
I always tell people it only takes money.
If you want to pony up the money to make some I'm sure someone could easily do it for you. But remember you will be the 100% financial support for the original planning & design, tooling and manufacturing and someone / several people's salary for it too.
I'm sure you could probably take one of those recorder making classes. Then you'll have one in wood, and would have the basic expertise. Then you'd have to get the tooling for metal cutting, drilling and go from there. Unless you want to use mandrels and shape sheets of aluminum/brass into shape.
Low whistles are most often metal, and some even have conical bores (and some recorders have cylindrical bores). But likely because of the lack of a market, the thin un-crossable line between a recorder and a whistle has kept a ten hole recorder from being made in brass/aluminium/carbon fiber/other things as a product.