Well, all the world's gold is worth about 8 trillion dollars.
All the world's silver is worth about 1 to 2 trillion dollars.
Not sure about platinum.
Also consider that the world reserve currency doesn't last forever, as we are seeing with the zenith of the U.S. Dollar. It's silly to expect that bitcoin would forever hold that top spot, and indeed, with the accelerating technological progress towards the singularity, bitcoin may well indeed be supplanted by Monero (which wouldn't be catastrophic).
Bitcoin and Monero fill two totally different needs. Bitcoin is a slow, lumbering blockchain that is completely public. It is wonderfully suited for large scale transfers between governments and businesses that people want to do openly. For this reason I would expect that bitcoin will become further centralized and the price must rise as well. The future "digital gold" will have some unique characteristics to it.
Monero will act as a perfect currency, and when nations or businesses need to transact in secret, this will be the one they turn to. I see no reason why bitcoin and Monero can't *both* be worth an XX-trillion dollar cap someday. Remember crypto isn't any asset class that has existed before it. It doesn't necessarily follow all the old rules.
It was very wise to set an initial limit of Monero at a number comparable to bitcoin's limit. This actually plays a psychological trick on the future public who just want things to be simple.... bitcoin is public and Monero is private.... both have about 20 million total macro-units. Therefore, to my simple monkey brain, it would follow that both should be valued at about 1:1.
Think of the Euro and Dollar, or the Euro and the Pound. These joust in value due to geographic restrictions, and it's likely that bitcoin and Monero may joust in value due to functional restrictions.
Honestly, I think that if (when) Monero rises to $2000 each, those who sell out of the majority of their stake are going to be cursing themselves for the rest of their life when it goes on to become one of the world reserve currencies by 2030 and is worth around $300,000 each.
Remember, money is made up, as is the value assigned to it. Monero is worth whatever people *believe* it is worth. And with the first private blockchain that can be accessed by the entire world? The value of these things as we go forward is going to dwarf any reasonable number that you think it should be valued at... simply because our monkey brains aren't equipped to deal with the ramifications of an entire species suddenly wanting the same scarce resource in a 10 year period.... this will go down in history as crypto-mania.... and will be the greatest wealth transfer in history.
You are fucking lucky to be reading this in 2015.
Now, what good are you going to do for the world with your wealth? Everyone is going to have seven wives and a waterfall pool, but don't be as selfish as the last crop of ultra-rich. Use your wealth to make our species better, and don't horde it like a bunch of fucking Smaugs.
Isn't silver's market cap less than 50 billion dollars?
http://rt.com/op-edge/silver-hedge-bitcoin-position-274/