There is no sweeter pleasure than to surprise a man by giving him more than he expected.

[Il n’est pas de plaisir plus doux que de surprendre un homme en lui donnant plus qu’il n’espère.]

Charles Baudelaire (1821-1867) French poet, essayist, art critic

Le Spleen de Paris (Petits Poèmes en Prose), No. 28 “The Counterfeit Money [La Fausse Monnaie]” (1869) [tr. Shipley (1919)]
    (Source)

(Source (French)). Alternate translations:

There is no sweeter pleasure than to surprise a man by giving him more than he expects.
[tr. Varèse (1970)]

There is no sweeter pleasure than surprising a man by giving him more than he hopes for.
[tr. Kaplan (1989)]