The main reason platinum parts cost more is because platinum
findings have a lot more precious metal in them than gold findings
do. Gold is generally alloyed with metals of lower value (silver,
copper and/or nickel), so the bulk of the cost of a 14K finding is
really only derived from its 58% gold content and the labor needed to
produce it. Platinum is usually alloyed with expensive metals like
iridium and ruthenium at a much higher level of purity, the most
common alloys contain 90% or 95% platinum. Alloyed gold also weighs
quite a bit less for a given volume than platinum alloys; the
specific gravity of 585 gold (14K) is about 13.5, and for 950
platinum it’s about 23.4. So a finding that weighs 1 pennyweight in
14K (@ 58% pure) might weigh 1.3 dwt in 950 platinum (@ 95% pure),
making the metal content in these example identical parts
approximately 0.6 dwt pure gold versus 1.2 dwt pure platinum.
Another contributing factor is that platinum is more difficult and
time-consuming to work with at just about every stage of production.
Starting with refining and then manufacturing findings or mill
products all the way to the end metalsmith, everyone that somehow
changes its form requires more time (and often more expensive
equipment) than when performing the same task with a gold alloy.
Consequently, the labor costs involved with platinum are higher at
virtually every stop along its way to a finished piece.
My opinion is that platinum is worth the extra cost compared to
white gold in almost every instance in which it is an option for
jewelry. Except for things like box clasp tongues, earring posts,
friction backs and other findings where its weight, sticky and
somewhat soft nature becomes an issue, platinum is almost always the
superior metal, especially when it is cold-worked into shape as
opposed to cast. I like to say it’s almost a magical metal. You can
sure work magic with it that you can’t with any other metal that I
know of, once you learn its properties.
Hope this helps!