My understanding is that white gold is created by mixing gold and palladium or even some platinum for the purposes of jewellery. This could make if more valuable (or costly) than rose gold (blended with copper).
I'm no metallurgist, but this also explains why WG is more expensive. On the negative, it's often plated with Rhodium which apparently needs to be re-applied through time so often people say WG isn't a good long-term metal for watches. I have only WG on my precious metal watches thus far and no problems but I haven't had them for decades.
Anybody else share that concern with WG?