Acts 7:16 (Byz2005) wrote:καὶ μετετέθησαν εἰς Συχέμ , καὶ ἐτέθησαν ἐν τῷ μνήματι ὃ ὠνήσατο Ἀβραὰμ τιμῆς ἀργυρίου παρὰ τῶν υἱῶν Ἐμμὸρ τοῦ Συχέμ.
and they were brought back to Shechem, and laid in the tomb that Abraham bought for a price in silver from the children of Hamor of Shechem.
The usual word for "to buy" is ἀγοράζειν, ἀγορᾶσαι, which is used of buying real property in
Matthew 13:44b (Byz2005) wrote:καὶ πάντα ὅσα ἔχει πωλεῖ, καὶ ἀγοράζει τὸν ἀγρὸν ἐκεῖνον.
and whatever he has, he sells, and buy that field.
The Seventy has
The verb κτᾶσθαι looks at the acquisition part of the buying and selling rather than the purchasing part of it, so far as I understand it.Joshua 24:32 wrote:καὶ τὰ ὀστᾶ Ιωσηφ ἀνήγαγον οἱ υἱοὶ Ισραηλ ἐξ Αἰγύπτου καὶ κατώρυξαν ἐν Σικιμοις ἐν τῇ μερίδι τοῦ ἀγροῦ οὗ ἐκτήσατο Ιακωβ παρὰ τῶν Αμορραίων τῶν κατοικούντων ἐν Σικιμοις ἀμνάδων ἑκατὸν καὶ ἔδωκεν αὐτὴν Ιωσηφ ἐν μερίδι
And the children of Israel brought up the bones of Joseph out of Egypt, and buried them in Shechem, in the inheritable tenure (the bounds of which were) the field which Jacob got of the sons of Hamor who dwelt in Shechem for a hundred lambs. And it was given to Joseph as an inheritable tenure.
My thoughts, as you can see from my translation of the Seventy, are that it could mean that Abraham got an enduring title for tomb in a technical legal sense, but I'm not sure that ὠνήσασθαι has that sense, but it is contextual. Alternatively, that verb could have been chosen to make it sound like a quote from an older text - ὠνήσασθαι being a recognisably older word instead of the contemporary ἀγοράζειν.
I am also unsure about the distinction between the common πωλεῖν (πωλῆσαι) "to sell" and the less frequent later form πιπράσκειν (πεπράκεναι, πραθῆναι), except that πιπράσκειν seems to be used in contexts that perhaps involve exchanging assets for liquidity, while πωλεῖν is closer to everyday barter like trading for an agreed value.
[Modern Greek uses πωλώ or πωλούμαι for sell and αγοράζω for buy.]