No, here it means "yes, you heard that correctly."
Yes, $1000 is a large amount of money. I'm sure you're surprised by how large the number is, and you think you might have misheard. But no, you heard it correctly--the number really is $1000.
"If you do this for me, I'll marry you. Yes, you heard me. I'll book a flight for our parents, and we can have the ceremony tomorrow."
"If you make him angry, he'll kill you. You heard me. He won't give you any warnings or second chances. He'll just pick up his sword and kill you."