Scorn for wealth among philosophers was at bottom a desire to avenge themselves against fate, by despising the very things of which she deprived them. It was a strategic way of avoiding the humiliations of poverty, a roundabout way of gaining an esteem they could not gain through wealth.

[Le mépris des richesses était dans les philosophes un désir cache de venger leur mérite de l’injustice de la fortune par le mépris des mêmes biens dont elle les privait; c’était un secret pour se garantir de l’avilissement de la pauvreté; c’était un chemin détourné pour aller à la considération qu’ils ne pouvaient avoir par les richesses.]

François VI, duc de La Rochefoucauld (1613-1680) French epigrammatist, memoirist, noble
Réflexions ou sentences et maximes morales [Reflections; or Sentences and Moral Maxims], ¶54 (1665-1678) [tr. Kronenberger (1959)]
    (Source)

This maxim appeared in the first edition, with various small modifications across subsequent editions.

(Source (French)). Alternate translations:

The contempt of wealth, in the Philosophers, was a secret desire of vindicating their merit, against the injustice of Fortune, by an affected slighting of those goods, whereof she depriv'd them. It was an humorous secret, which they had found out, to indemnifie themselves from the disparagement accessory to Poverty. In fine, it was a winding path, or by-way to get into that esteem, which they could not obtain by Riches.
[tr. Davies (1669), ¶170]

When the Philosophers despised Riches, it was because they had a mind to vindicate their own Merit, and take a Revenge upon the injustice of Fortune, by vilifying those Enjoyments which She had not given them: This was a secret to ward off the Contempt that Poverty brings, a kind of winding By-path to get into the Esteem of the World, and when Riches had not made them considerable, to make themselves so some other way.
[tr. Stanhope (1694), ¶55]

The contempt of riches in the philosophers was a concealed desire of revenging on Fortune the injustice done to their merit, by despising the good she denied them. It was a secret to shelter them from the ignominy of poverty ; a bye-way to arrive at the esteem they could not procure by wealth.
[pub. Donaldson (1783), ¶341; ed. Lepoittevin-Lacroix (1797), ¶54]

Contempt of riches in the old philosophers was a concealed desire of revenge, by despising the good which Fortune had denied them. It was an artful shelter from the disgrace of poverty: a by-way to arrive at that esteem which they could not procure by wealth.
[ed. Carville (1835), ¶301]

The contempt of riches among the philosophers was a hidden desire to revenge their merit for the injustice of Fortune, by contempt of the very advantages of which she deprived them. It was a secret to secure themselves from the degradation of poverty: it was a by road to arrive at that consideration which they could not obtain by riches.
[ed. Gowens (1851), ¶55]

The contempt of riches in philosophers was only a hidden desire to avenge their merit upon the injustice of fortune, by despising the very goods of which fortune had deprived them; it was a secret to guard themselves against the degradation of poverty, it was a back way by which to arrive at that distinction which they could not gain by riches.
[tr. Bund/Friswell (1871)]

The Philosophers' scorn of wealth was but their secret ambition to exalt their merit above fortune by deriding those blessings which Fate denied them. It was a ruse to shield them from the sordidness of poverty, and a subterfuge to attain that distinction which they could not achieve by wealth.
[tr. Heard (1917)]

Contempt of wealth was, among the early philosophers, due to a secret desire to vindicate their worth agaiunst the malignity of fate, by affecting to despise those very gifts of which it deprived them. It was a means of insurance against the ignominy of poverty, a round-about way of acquiring the esteem they were unable to command by the possession of wealth.
[tr. Stevens (1939)]

Philosophers have expressed their contempt for material riches; they thus reveal their wish to vindicate their merit on their fate by displaying their contempt for those gifts which fate has withheld from them; it is a secret remedy to save them from those degradations which poverty entails; it is also an indirect method for obtaining that respect which they cannot gain through wealth.
[tr. FitzGibbon (1957)]

The scorn for riches displayed by the philosophers was a secrete desire to recompense their own merit for the injustice of Fortune by scorning those very benefits she had denied them; it it was a private way of remaining unsullied by poverty, a devious path towards the high respect they could not command by wealth.
[tr. Tancock (1959)]

The contempt which philosophers professed for wealth, was but a hidden desire of getting revenge for their merit upon the injustice of Fortune, by despising those goods of which she had deprived them: it was a secret by which to protect themselves against the degradation of poverty; it was an alternate path by which to gain that consideration which they had not been able to attain through riches.
[tr. Whichello (2016)]