Which is why my first car had CSP wide5 discs(aluminum hub/iron caliper). My new car has Airkewld wide5 discs, which has a two piece billet aluminum hub, both pieces are about 1/2" thick aluminum. The caliper is a Wilwood 4 piston, SUPER light.
Both kits have iron rotors, but that's expected.
That EMPI/Socal kit is ALL IRON, all of it. REALLY a boat anchor on each corner.