Plato, Laws 921b

τῷ πωλοῦντι συνεβούλευεν, μὴ πλέονος τιμᾶν διαπειρώμενον ἀλλʼ ὡς ἁπλούστατα τῆς ἀξίας, ταὐτὸν δὴ προστάττει καὶ τῷ ἀναιρουμένῳ—γιγνώσκει γὰρ ὅ γε δημιουργὸς τὴν ἀξίαν —ἐν ἐλευθέρων οὖν πόλεσιν οὐ δή ποτε χρὴ τέχνῃ, σαφεῖ τε καὶ ἀψευδεῖ φύσει πράγματι, διαπειρᾶσθαι τῶν ἰδιωτῶν τεχνάζοντα αὐτὸν τὸν δημιουργόν, δίκας δὲ εἶναι τούτων τῷ ἀδικουμένῳ πρὸς τὸν ἀδικοῦντα. ἐὰν δέ τις ἐκδοὺς αὖ

so the law counsels the contractor who undertakes a work not to give in too high an estimate for it, but to estimate it simply at its real worth; this same charge the law gives, I say, to the contractor, for he as a craftsman certainly knows what its worth is. In States composed of gentlemen it is wrong for a craftsman to try by his art (which is essentially truthful and sincere) to impose artfully upon lay persons; and in such cases the wronged shall be entitled to prosecute the wrongdoer. If, on the other hand, a man who has given an order to a craftsman