Ple-Sen
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1) Create a character with 10 charisma.
2) Take the "Ixianism" perk (resulting in 14 charisma).
3) Choose the "Good Manners" perk (+4 to etiquette and charm).
4) Select the Astria origin (+4 to etiquette and +50% to trade effectiveness).
5) This results in ((14+4)x2+4)x1.5 = a 60% discount.