I think that it's not that inappropriate - the prize will be released once the value rises to the amount stated, which if/when it occurs the $1m will be worth $1b. They're even being transparent in stating that the current amount was $1m invested, so nobody should be under the false impression that they have $1b at this immediate moment to give away.

RE: 5% rate increase - it's simply the modification of the price feed each year, there is no other external factor required to ensure this 5% rise occurs.