Just my 1 cent but I think a brass radiator will outlast any modern vehicle that it’s installed in and it’s quite likely any notions that modern cars will kill a brass radiator are fairy tales. My hot rod Ford has a brass radiator that’s been in there for half a dozen years with no problems at all.
The other half of my 2 cents is that a plastic/aluminum radiator is much cheaper and easier to manufacture; which is it in a nutshell.
I do some machine work on the metal lathe and mill and cringe whenever I have to buy a piece of brass stock. The last piece I bought from the aircraft salvage (about 8" long X 2" in diameter) set me back about 25 bucks if I remember correctly. It’s pricy.
A couple of years ago someone broke into a local scrap iron building one weekend by cutting a hole in the wall. They used the forklift to load several barrels of brass scrap onto a trailer or truck and those few barrels were valued at about 5 grand.