All luxury corrupts either the morals or the taste.

[Tout luxe corrompt ou les mœurs ou le goût.]

Joseph Joubert (1754-1824) French moralist, philosopher, essayist, poet

Pensées [Thoughts], ch. 16 “Des Mœurs publiques et privées; du Caractère des Nations [On Morality and the Character of Nations],” ¶ 38 (1850 ed.) [tr. Calvert (1866), ch. 12]
    (Source)

(Source (French)). Alternate translations:

All luxury corrupts either conduct or taste.
[tr. Lyttelton (1899), ch. 15, ¶ 15]

Every form of extravagance corrupts either one's morals or one's taste.
[tr. Collins (1928), ch. 15]