If you think about it, 100 ME is enough to do 1.5 tier runs, since you only use 10 energy per elevator and can still have 10 ME left over after doing 9 floors, provided you don't mess up. What this does is this gives people a lot of crowns, especially if, say, they do tier 2 or 3 repeatedly. By reducing ME to, let's say, 70, you could have less tier runs before running out of ME. For OOO, this means that those who want to do continuous runs would also have to spend for more CE. For players, this means less tier runs, less crown influx in the economy and therefore, cheaper CE prices.