It’s a lump of metal that sits between the wheel and the hub, how good does it need to be?! No need to be daft about it with the plastic comment, but there’s no need to spend silly money on uber-lightweight forged items when some cnc alloy spacer will do the exact same job, unless of course you’re all about the weight saving and are running carbon fibre wheels. And if you are then good for you, but for 99% of people there is no point spending a fortune on something so basic.
Besides, if you already have your perfect spacer, then you wouldn’t be looking at these as you’ve clearly done your research.