“in the hearing of the people of the land.” Abraham, the wise negotiator, makes the deal in a loud enough voice that everyone can hear it.
“price.” The Hebrew is “silver.”
“Take it from me.” In other words, “Accept it from me.” Abraham knows the deal is not done until Ephron takes the silver. Then everyone knows the cave is sold. It is always good in negotiations if something physical changes hands; that avoids misunderstandings and “he said she said” later. The wisdom of the transfer of something physical was passed down in the culture and we see in the time of the Judges that one person gave the other his sandal (Ruth 4:7-9).