How many of the 600k Mastercoins have already been mined? Are they mined the way BTC is mined or they created in some other way? Where can one buy these Mastercoins? How was the valuation: 600k Mastercoins = 12k BTC arrived at?
Mastercoins were made by sending bitcoins to the exodus address between 31 July - 31 Aug. Every bitcoin sent earned the sender 100 Mastercoins + a bonus (10-40% depending on how early you sent them. early bird bonus). All the bitcoins sent made all the mastercoins that are ever going to exist. Roughly 600k mastercoins were "made" and that will be the total number for ever and ever. (+10% for the foundation but maybe that has already been factored in?).
So there is no mining. Right now the only way to buy mastercoins is from another person who has them (there isn't yet an exchange). Im not sure but my guess is that the current valuation is a rough estimate that the price of mastercoin has doubled (50 coins for 1 btc)