I have determined that the Mushroom Kingdom's economy is disasterous, and wickedly unstable.
In the beginning of the game, 100 Mushroom coins were 10 BeanBean coins. In the middle of it, 99,999,999,999,999 (I think that was the number) Mushroom coins were 99 BeanBean coins, an inflation of about 1,000,000,000x. If the princess getting kidnapped really messes up the economy that much, I (Or, better still, an imaginary version of me living in Mario's world at the time) could make a HUGE fortune hoarding BeanBean coins and exchanging them for Mushroom coins when the princess is kidnapped, then re-exchanging after Mario/Luigi/Booster (You never know) saves her.
Wow, that was a bit tangential.
~I.S.~