“I am rather tame concerning the possession of other things but nearly erotic when it comes to acquiring friends.”
ἐγὼ δὲ πρὸς μὲν ταῦτα πρᾴως ἔχω, πρὸς δὲ τὴν τῶν φίλων κτῆσιν πάνυ ἐρωτικῶς
In this dialogue Plato’s Socrates is voluble about the importance of friends (if we take him seriously)
Wisdom makes people want to be your friend:
Plato, Lysis 210d
“If you are wise, then everyone will be your family and friend.”
ἐὰν μὲν ἄρα σοφὸς γένῃ, ὦ παῖ, πάντες σοι φίλοι καὶ πάντες σοι οἰκεῖοι ἔσονται
(Because you are useful and good)
And a friend is much more important than wealth:
Plato, Lysis 211e5-6
“I would much rather acquire a friend than all of Darius’ gold.”
οἶμαι δέ…μᾶλλον ἢ τὸ Δαρείου χρυσίον κτήσασθαι δεξαίμην πολὺ πρότερον ἑταῖρον
A sweet sentiment certainly, but typically undermined by Socrates’ claims soon thereafter that he doesn’t understand how men become friends of one another. Poor Socrates, he’s like Polyphemos who loves Galatea: she’s a sea nymph and he can’t swim.
(See the full text here.)
And Socrates would probably be disappointed by the later wisdom on friendship from someone like Ovid:
Ovid, Epistulae ex Ponto 2.3.7-8
“It is shameful to say, but — if truth be told — most people value their friendships on utilitarian grounds”.
Turpe quidem dictu, sed – si modo uera fatemur –
uulgus amicitias utilitate probat.
Well, it is Ovid. Ovid is pretty much always mercenary and sordid.