Quick efficiency cost for buying shit in the monolith to maximize points.
Basically enhancement machine up to 180, anything that is on sale, and notes are more efficient than buying potentials for points.
Note that each level of harmony skill is 120 as well, so one strat for difficulty 5 monolith runs is to go all in on notes and only go for key potentials, you need to keep the refreshes for the final shop to get more notes. Hitting lvl 25 for record level is an extra 1000 atk boost compared to lvl 24.