75% is only an example. Adjust according to what you can actually manage to save. If you are paid $100k, as is by no means impossible for this demographic (and in fact is rather easy if you're a two-income household)m then 75% is easily doable. At $25k, which is also by no means impossible for our demographic, then yes, the 75% savings rate becomes difficult.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.