Money makes the world go around...
Therefore money is spin and spin is money.
(Originally there was much more use of RPM as currency, as RPM didn't reset after battles [Perils could be paid for with RPM too for an example], but 1) it allowed you to cheese the game by charging forever against the bosses that aren't fights 2) after enough DP increases, retaining it also made you cheese through every boss. Once I decided to make it reset, the characters and things that asked for great amounts of your RPM for skills/services also had to be done with because it didn't work anymore. Glad I noticed that issue halfway through as opposed to near completion, but still a bummer to have to rework/remove so many things due to one system change.)