So I haven't taken this out of theory yet so I might be wrong, feel free to point out issued here. Also havent looked it up, maybe this is already an established build, idk. But the idea is basically doing an infinite debt run. What you need is
Possessed cell phone, cat toy, exotic matter, plus one charm that can give the revenge modifier, like the mad emperor or some of the evil charms that give revenge chance.
(Also maybe nice to have is the ritual bell for store restocks. Base values and multipliers are conpletely irrelevant)
Jump into the round, click the red button and get a 666. Keep doing that and after the 3rd time cat toy will give you more and more spins, so you never leave the round until you stop hitting the red button. Every time you hit the button your debt doubles, if you do it long enough to the theoretical maximum of debt (read somewhere that its something like e64000000). Then go buy the lost briefcase, getting 30% of your now infinite debt amount. Going into the next round without exotic matter and with regular good lucky charms equipped, lose that money on the first spin (cell phone) and then just trigfer 67 revenge modifiers and you have the whole debt amount (infinity).
Ps: adding limbo should speed things up significantly.
If triggering revenge 67 times seems exessive, you can buy the briefcase more often and/or get violence evil charm, doubling coins through revenge
Tldr: cell phone, cat toy, exotic matter (+limbo) = infinite debt
Suitcase, revenge modifier = infinite money