I agree the look nice but will probably be quite heavy, no?
I remember one of the reasons my dad removed the centre caps from his Fiat 127 was to reduce unsprung weight. I couldn't believe it until I lifted one of them, they weighted a ton, they were quite more chunky than the ones you have pictured though.
Not as light as a packet of crisps, but as it's just pressed Stainless-steel they're pretty light indeed, but strong.
Get the wheels on already!