Abusing purification during the festival can make the festival of greed net-negative on corruption. Less corruption means you have more leeway when it comes to your blessed water and drugs situation. Blue sugar+ means you don't have to spend as much gold and ether at the alchemist, which in turn lets you spend ether instead of gold to learn fire/wind slime and/or skip out on some Nephlune ether restocks.
Post-festival after you use your remaining days before withdrawal hits to win duels and stat-check the bridge bandits is a good time to spend at the blacksmith to grind your health back up. Withdrawal II turns into addiction II and back into withdrawal II, so taking drugs once withdrawal III fades into II creates a good window to kill some more bosses before addiction becomes withdrawal again. Drug addiction is not that dissimilar from managing daily willpower loss, with an addict's blue sugar+ being like a curse victim's blessed water.
There is an theoretical route through which you can do a no-sk Belphegor and Sathanas before their timers and that's fine. I prefer to just star knightess those assholes precisely so I have more wiggle room to take advantage of the blacksmith salary during pure runs. But while I'll agree that 38 workdays is a long time to break even(AuraDev, buff to +25 per star metal please), you should absolutely have the time to break even if you burn for purification during the festival.
Once you unlock vice on your pink run, the save the crops quest gives you the option to demand daily payments from the Riverflow farmers by threatening to withhold the only way to save their livelihood if they don't agree with your demand. This is a form of extortion.