[citation][nom]deksman[/nom]It can be man-made though (which is done now) by bombarding uranium-235 (abundant in nature) with thermal neutrons.My point was that for most if not all our needs, we can make whatever we need in more than sufficient quantities here on Earth.We had the technology for reconstituting matter from one form into another one for some time now.It can still be used for industrial (and other) purposes. As for it being 'expensive'... only in monetary value. From a technological/resource/manpower point of view (without bringing money into the equation at all), it can be done with relative ease (as can be many other things).Besides, I personally couldn't care less about gold necklaces or similarly useless trinkets.[/citation]
That's some pretty big hand waving you're doing there. Time is money as the saying goes and money is really time, and energy, and resources. When you spend money on something, you're trading something we've arbitrarily decided is worth a certain perceived value for something else that has a perceived value to you. That widget you buy is made from resources, energy and someone else's time and you're paying money that you've been given because you've devoted your time and resources towards making something else (e.g. working at your job, growing crops, etc). Even if you were to hand-wave away the existence of money, you still need to trade something of value to be given something else of value. You're going to have to trade me a lot of grain before I give you a single gram of man-made Platinum, Palladium or Rhodium.
Yes, we can use nuclear neutron decay to make rare earth metals, but that doesn't mean we have an unlimited supply as a result. We can't just make platinum from any 'ol random atoms we have sitting around, only a few particular isotopes can be irradiated with neutron decay that will eventually decay to a stable form of platinum and those isotopes too are in a limited supply.
Supply issues don't even factor in the headache of separating the final product from all the side products you don't want, which is usually the majority of the cost of pretty much anything made (as a ChE example, PFTRs and CSTRs cost pennies to make vs the cost of operating pretty much any separations unit such as a distillation column or liquid liquid extractor). Sure, you can irradiate Ir-191 and Ir-193 and your final product is going to include Pt-192 and Pt-194 and a bunch of other by-products and some remaining raw materials. You're going to have to expend significant amounts of energy separating those either using gas centrifuges, using ionic chemistry, or some form of reversible column system, all of which take energy, resources and have a waste stream. Entropy is a bitch, and you need to expend energy overcoming it. If manufacturing rare earths was really so 'relatively easy', as you put it, we'd be doing it rather than trying to dig something found at 5 ppb out of the earth's crust.
Finally, Uranium-235 is not abundant, it makes up less than 1% or Uranium (which is at about 4 ppm in the soil), so you'd have to purify and separate that too before you can even begin your nuclear alchemy because 238 decays via useless alpha radiation.