Ok. If you want to use this analogy. So if Mastercoin is the gold, then what are the user defined coins defined in Mastercoin?
Maybe Bitcoin is the ferry, Mastercoin is the container, and the gold is in the user defined coins.
What value does one place on this 'mastercoin' gold. We know the value of bitcoin is based on the energy and resources to extract a bitcoin. How much did it cost to extract this Mastercoin gold?
I think that you're trying to say that user-defined currencies do not create additional demand for Mastercoin, and thus do not increase its value.
It is true, to a certain extent. (They make Mastercoin more useful no more than they make Bitcoin more useful.)
However, you're missing that demand for mastercoins can come from other directions: mastercoin provides features which work only for mastercoin-based currencies, and mastercoin is probably the biggest mastercoin-based currency, so people will use it.
Particularly, escrow-based currencies and CFDs: when/if these features will be in use, you'll need some mastercoins to use as an escrow/collateral for CFD. If there is a large CFD market, (e.g. suppose it requires $1B of value in collateral), mastercoin "market cap" will also be large.
if one master coin can contain the same number of user defined coins as 100 master coins, then what is it worth?
You seem to be missing the fact that mastercoin itself will be used as a currency. Would you rather use Mastercoin which has $200M market cap, or some shoddy "user defined coins"?
"User defined coins" is not the only feature.