68 volumes with a minimum cost of 57 euro (roughly, and some were more) comes to 3876 euro, or a little over $5,000.
I also have a lot of Loeb library volumes (54 red or Latin volumes, and 122 green or Greek volumes), but I think that replacing the Pléiade volumes in the event of loss would be much more difficult. However, in an absolute sense, assuming the list price of $24 per volume (though Amazon frequently sells them at a dollar or two discount), it comes close at a list value of $4224.
If I consider the Dumbarton Oaks and I Tatti books as in the same "series" as Loeb, considering that they are supposed to be chronological continuations of the series, then I have 33 more books (20 I Tatti and 13 Dumbarton Oaks) at $30 a piece, which brings the total from $4224 to $5214. But again, all of those books could be reordered.
I also have the complete "Mysteries of the Unknown" series from Time-Life in mint condition, which I assume would be almost impossible to replace given that it has been out of print for some time.
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*