1)
Why did Avraham prostrate himself before "Am ha'Aretz"?
1.
Seforno: As a mark of thanks, as if it was because of them that Efron was willing to enter into an agreement with him.
2.
Ha'amek Davar: He was thankful to the Am ha'Aretz for helping persuade Efron to sell. He was not thankful to Bnei Ches, for he understood their guile (to make him pay an exorbitant amount).
